共用题干
New Understanding of Natural Silk's Mysteries
Natural silk,as we all know,has a strength that man-made materials have long struggled to match.In a
discovery that sounds more like an ancient Chinese proverb than a materials science breakthrough,MIT re-
searchers have discovered that silk gets its strength from its weakness.Or,more specifically,its many weak-
nesses. Silk gets its extraordinary durability and ductility（柔韧性）from an unusual arrangement of hydrogen
bonds that are intrinsically very weak but that work together to create a strong,flexible structure.
Most materials一especially the ones we engineer for strength一get their toughness from brittleness.As
such,natural silks like those produced by spiders have long fascinated both biologists and engineers because of
their light weight,ductility and high strength(pound for pound,silk is stronger than steel and far less brittle).
But on its face,it doesn't seem that silks should be as strong as they are;molecularly,they are held together by
hydrogen bonds , which are far weaker than the covalent（共价的）bonds found in other molecules.
To get a better understanding of how silk manages to produce such strength through such weak bonds,
the MIT team created a set of computer models that allowed them to observe the way silk behaves at the
atomic level. They found that the arrangement of the tiny silk nanocrystals（纳米晶体）is such that the hydro-
gen bonds are able to work cooperatively,reinforcing one another against external forces and failing slowly
when they do fail,so as not to allow a sudden fracture to spread across a silk structure.
The result is natural silks that can stretch and bend while retaining a high degree of strength.But while
that's all well and good for spiders,bees and the like,this understanding of silk geometry could lead to new
materials that are stronger and more ductile than those we can currently manufacture.Our best and strongest
materials are generally expensive and difficult to produce(requiring high temperature treatments or
energy-intensive processes).
By looking to silk as a model,researchers could potentially devise new manufacturing methods that rely
on inexpensive materials and weak bonds to create less rigid,more forgiving materials that are nonetheless
stronger than anything currently on offer. And if you thought you were going to get out of this materials
science story without hearing about carbon nanotubes（纳米碳管）, think again. The MIT team is already in
the lab looking into ways of synthesizing silk-like structures out of materials that are stronger than natural
silk-like carbon nanotubes. Super-silks are on the horizon.
If the hydrogen bonds break due to external forces,they break fast.
A:Right
B:Wrong
C:Not mentioned
New Understanding of Natural Silk's Mysteries
Natural silk,as we all know,has a strength that man-made materials have long struggled to match.In a
discovery that sounds more like an ancient Chinese proverb than a materials science breakthrough,MIT re-
searchers have discovered that silk gets its strength from its weakness.Or,more specifically,its many weak-
nesses. Silk gets its extraordinary durability and ductility（柔韧性）from an unusual arrangement of hydrogen
bonds that are intrinsically very weak but that work together to create a strong,flexible structure.
Most materials一especially the ones we engineer for strength一get their toughness from brittleness.As
such,natural silks like those produced by spiders have long fascinated both biologists and engineers because of
their light weight,ductility and high strength(pound for pound,silk is stronger than steel and far less brittle).
But on its face,it doesn't seem that silks should be as strong as they are;molecularly,they are held together by
hydrogen bonds , which are far weaker than the covalent（共价的）bonds found in other molecules.
To get a better understanding of how silk manages to produce such strength through such weak bonds,
the MIT team created a set of computer models that allowed them to observe the way silk behaves at the
atomic level. They found that the arrangement of the tiny silk nanocrystals（纳米晶体）is such that the hydro-
gen bonds are able to work cooperatively,reinforcing one another against external forces and failing slowly
when they do fail,so as not to allow a sudden fracture to spread across a silk structure.
The result is natural silks that can stretch and bend while retaining a high degree of strength.But while
that's all well and good for spiders,bees and the like,this understanding of silk geometry could lead to new
materials that are stronger and more ductile than those we can currently manufacture.Our best and strongest
materials are generally expensive and difficult to produce(requiring high temperature treatments or
energy-intensive processes).
By looking to silk as a model,researchers could potentially devise new manufacturing methods that rely
on inexpensive materials and weak bonds to create less rigid,more forgiving materials that are nonetheless
stronger than anything currently on offer. And if you thought you were going to get out of this materials
science story without hearing about carbon nanotubes（纳米碳管）, think again. The MIT team is already in
the lab looking into ways of synthesizing silk-like structures out of materials that are stronger than natural
silk-like carbon nanotubes. Super-silks are on the horizon.
If the hydrogen bonds break due to external forces,they break fast.
A:Right
B:Wrong
C:Not mentioned
He was banned from driving for six months.
A:listed
B:forbidden
C:handled
D:investigated
A:listed
B:forbidden
C:handled
D:investigated
共用题干
Free Statins with Fast Food could Neutralize Heart Risk
Fast food outlets could provide statin drugs free of1so that customers can reduce the heart disease dangers of fatty food,researchers at Imperial College London 2in a new study.
Statins reduce the3of unhealthy“LDL” cholesterol in the blood. A wealth of trial data has proven them to be highly effective at lowering a person's heart attack4.
In a paper published in the American Journal of Cardiology,Dr Darrel Francis and colleagues calculate that the reduction in heart attack risk offered by a statin is5to offset the increase in heart attack risk from6a cheeseburger and drinking a milkshake.
Dr Francis,from the National Heart and Lung Institute at Imperial College London,who is the senior author of the study,said:“Statins don't cut out all of the7effects of cheeseburgers and French fries. It's better to avoid fatty food altogether. But we've worked out that in terms of your8of having a heart attack. Taking a statin can reduce your risk to more or less the same9 as a fast food meal increases it.”“It's ironic that people are free to take as many unhealthy condi-ments in fast food outlets as they10,but statins,which are beneficial to heart health,have to be prescribed. It makes sense to make risk-reducing statins available just as easily as the unhealthy condiments that are 11 free of charge. It would cost less than 5 pence per/u>12一not much different to a sachet of sugar.”Dr Francis said.
When people engage in risky behaviours like driving or smoking,they're encouraged to take13that lower their risk,like14a seatbelt or choosing cigarettes with filters.
Taking a statin is a rational way of15some of the risks of eating a fatty meal.
1._________
A: change
B: charge
C: chain
D: chance
Free Statins with Fast Food could Neutralize Heart Risk
Fast food outlets could provide statin drugs free of1so that customers can reduce the heart disease dangers of fatty food,researchers at Imperial College London 2in a new study.
Statins reduce the3of unhealthy“LDL” cholesterol in the blood. A wealth of trial data has proven them to be highly effective at lowering a person's heart attack4.
In a paper published in the American Journal of Cardiology,Dr Darrel Francis and colleagues calculate that the reduction in heart attack risk offered by a statin is5to offset the increase in heart attack risk from6a cheeseburger and drinking a milkshake.
Dr Francis,from the National Heart and Lung Institute at Imperial College London,who is the senior author of the study,said:“Statins don't cut out all of the7effects of cheeseburgers and French fries. It's better to avoid fatty food altogether. But we've worked out that in terms of your8of having a heart attack. Taking a statin can reduce your risk to more or less the same9 as a fast food meal increases it.”“It's ironic that people are free to take as many unhealthy condi-ments in fast food outlets as they10,but statins,which are beneficial to heart health,have to be prescribed. It makes sense to make risk-reducing statins available just as easily as the unhealthy condiments that are 11 free of charge. It would cost less than 5 pence per/u>12一not much different to a sachet of sugar.”Dr Francis said.
When people engage in risky behaviours like driving or smoking,they're encouraged to take13that lower their risk,like14a seatbelt or choosing cigarettes with filters.
Taking a statin is a rational way of15some of the risks of eating a fatty meal.
1._________
A: change
B: charge
C: chain
D: chance
共用题干
An Intelligent Car
Driving needs sharp eyes, keen ears, quick brain, and coordination（协调）between
hands and the brain.Many human drivers have all_________(1)and can control a fast
-moving car. But how does an intelligent car control itself?
There is a virtual（虚拟的）driver in the smart car. This virtual driver has "eyes",
"brains","hands"and"feet",too.The minicameras_________(2)each side of the
car are his"eyes",which_________(3)the road conditions ahead of it.They watch
the_________(4)to the car's left and right.There is also a highly automatic driving
_________(5)in the car. It is the built-in computer,which is the virtual driver's
"brain".His"brain"_________(6)the speeds of other moving cars near it and
analyzes their positions.Basing on this information,it chooses the_________(7)path
for the intelligent car,and gives instructions to the"hands"and"feet"to act accordingly.
In this way,the virtual driver_________(8)his car.
What is the virtual driver's best advantage?He reacts_________(9).The
minicameras are bringing_________(10)continuously to the"brain".It completes the
processing of the images within 100 milliseconds._________(11),the world's best
driver needs at least one second to react.Besides,when he takes_________(12),he
needs one more second.
The virtual driver is really wonderful.He can reduce the accident_________(13)
considerably on expressways（高速公路）.In this_________(14),can we let him have
the wheel at any time and in any place?Experts_________(15)that we cannot do that
just yet.His ability to recognize things is still limited.He can now only drive an intelligent
car on expressways.
_________(3)
A:change
B:observe
C:improve
D:meet
An Intelligent Car
Driving needs sharp eyes, keen ears, quick brain, and coordination（协调）between
hands and the brain.Many human drivers have all_________(1)and can control a fast
-moving car. But how does an intelligent car control itself?
There is a virtual（虚拟的）driver in the smart car. This virtual driver has "eyes",
"brains","hands"and"feet",too.The minicameras_________(2)each side of the
car are his"eyes",which_________(3)the road conditions ahead of it.They watch
the_________(4)to the car's left and right.There is also a highly automatic driving
_________(5)in the car. It is the built-in computer,which is the virtual driver's
"brain".His"brain"_________(6)the speeds of other moving cars near it and
analyzes their positions.Basing on this information,it chooses the_________(7)path
for the intelligent car,and gives instructions to the"hands"and"feet"to act accordingly.
In this way,the virtual driver_________(8)his car.
What is the virtual driver's best advantage?He reacts_________(9).The
minicameras are bringing_________(10)continuously to the"brain".It completes the
processing of the images within 100 milliseconds._________(11),the world's best
driver needs at least one second to react.Besides,when he takes_________(12),he
needs one more second.
The virtual driver is really wonderful.He can reduce the accident_________(13)
considerably on expressways（高速公路）.In this_________(14),can we let him have
the wheel at any time and in any place?Experts_________(15)that we cannot do that
just yet.His ability to recognize things is still limited.He can now only drive an intelligent
car on expressways.
_________(3)
A:change
B:observe
C:improve
D:meet
An Essential Scientific Process
All life on the earth depends upon green plants. Using sunlight, theplants produce their own food. Then animals feed upon the plants. They take inthe nutrients the plants have madested. But that’s not all.Sunlight also helps a plant produce oxygen. Some of the oxygen is used by theplant, but a plant usually produces me oxygen than it uses. The excess oxygenis necessary f animalsother ganisms to live.
The process of changing light into foodoxygen is calledphotosynthesis. Besides light energy from the sun, plants also use water carbon dioxide. The water gets to the plant through its roots. The carbondioxide enters the leaves through tiny openings called stomata. The carbondioxide travels to chloplasts, special cells in the bodies of green plants.This isphotosynthesis takes place. Chloplasts contain the chlophyllsthat give plants their green col. The chlophylls are the molecules thattrap light energy. The trapped light energy changes watercarbon dioxide toproduce oxygena simple sugar called glucose.
Carbon dioxideoxygen move intoout of the stomata. Watervap also moves out of the stomata. Me than 90 percent of water a planttakes in through its roots escapes through the stomata. During the daytime, thestomata of most plants are open. This allows carbon dioxide to enter the leavesf photosynthesis. As night falls, carbon dioxide is not needed. The stomataof most plants close. Water loss stops.
If photosynthesis ceased, there would be little foodother ganicmatter on the earth. Most ganisms would disappear. The earth’s atmospherewould no longer contain oxygen. Photosynthesis is essential f life on ourplanet.
词汇：
nutrient n.营养物
ganism n.生物体，有机体
carbon dioxide n.二氧化碳
chloplast n.叶绿体
molecule n.分子
vap n.水蒸气
oxygen n.氧气
photosynthesis n.光合作用
chlophyll n.叶绿素
glucose n.葡萄糖
cease v.停止
注释：
1.Then animals feed upon the plants.动物以植物为食。
练习：
1.In the first paragraph，the wd “excess” means
A.heavy.
B.extra.
C.green.
D.liquid.
All life on the earth depends upon green plants. Using sunlight, theplants produce their own food. Then animals feed upon the plants. They take inthe nutrients the plants have madested. But that’s not all.Sunlight also helps a plant produce oxygen. Some of the oxygen is used by theplant, but a plant usually produces me oxygen than it uses. The excess oxygenis necessary f animalsother ganisms to live.
The process of changing light into foodoxygen is calledphotosynthesis. Besides light energy from the sun, plants also use water carbon dioxide. The water gets to the plant through its roots. The carbondioxide enters the leaves through tiny openings called stomata. The carbondioxide travels to chloplasts, special cells in the bodies of green plants.This isphotosynthesis takes place. Chloplasts contain the chlophyllsthat give plants their green col. The chlophylls are the molecules thattrap light energy. The trapped light energy changes watercarbon dioxide toproduce oxygena simple sugar called glucose.
Carbon dioxideoxygen move intoout of the stomata. Watervap also moves out of the stomata. Me than 90 percent of water a planttakes in through its roots escapes through the stomata. During the daytime, thestomata of most plants are open. This allows carbon dioxide to enter the leavesf photosynthesis. As night falls, carbon dioxide is not needed. The stomataof most plants close. Water loss stops.
If photosynthesis ceased, there would be little foodother ganicmatter on the earth. Most ganisms would disappear. The earth’s atmospherewould no longer contain oxygen. Photosynthesis is essential f life on ourplanet.
词汇：
nutrient n.营养物
ganism n.生物体，有机体
carbon dioxide n.二氧化碳
chloplast n.叶绿体
molecule n.分子
vap n.水蒸气
oxygen n.氧气
photosynthesis n.光合作用
chlophyll n.叶绿素
glucose n.葡萄糖
cease v.停止
注释：
1.Then animals feed upon the plants.动物以植物为食。
练习：
1.In the first paragraph，the wd “excess” means
A.heavy.
B.extra.
C.green.
D.liquid.
I will draft a letter for you.
A:clarify
B:formulate
C:revise
D:contribute
A:clarify
B:formulate
C:revise
D:contribute
共用题干
Global Warming
Few people now question the reality of global warming and its effects on the world's climate. Many scientists1the blame for recent natural disasters on the increase2the world's temperatures and are convinced that,more than3before,the Earth is at4from the forces of the wind,rain and sun.5to them,global warming is making extreme weather events,6as hurricanes and droughts,even more7and causing sea levels all around the world to8.
Environmental groups are putting9on governments to take action to reduce the 10 of carbon dioxide which is given 11 by factories and power plants,thus attacking the problem at its source. They are in12of more money being spent on research into so-lar,wind and wave energy devices,which could then replace existing power13.
Some scientists,14believe that even if we stopped releasing carbon dioxide and other gases into the atmosphere tomorrow,we would have to wait15hundred years to notice the results. Global warming,it seems,is here to stay.
15._________
A: several
B: over
C: numerous
D: various
Global Warming
Few people now question the reality of global warming and its effects on the world's climate. Many scientists1the blame for recent natural disasters on the increase2the world's temperatures and are convinced that,more than3before,the Earth is at4from the forces of the wind,rain and sun.5to them,global warming is making extreme weather events,6as hurricanes and droughts,even more7and causing sea levels all around the world to8.
Environmental groups are putting9on governments to take action to reduce the 10 of carbon dioxide which is given 11 by factories and power plants,thus attacking the problem at its source. They are in12of more money being spent on research into so-lar,wind and wave energy devices,which could then replace existing power13.
Some scientists,14believe that even if we stopped releasing carbon dioxide and other gases into the atmosphere tomorrow,we would have to wait15hundred years to notice the results. Global warming,it seems,is here to stay.
15._________
A: several
B: over
C: numerous
D: various
The article sketched the major events of the decade.
A:described
B:offered
C:outlined
D:presented
A:described
B:offered
C:outlined
D:presented
共用题干
Homosexuals（同性恋者）
Many homosexuals prefer to be called gay or,for woman,lesbian.Most of them live quiet lives just______(51)anyone else.Some gay people have always raised children,______(52)or with partners,and the use of artificial insemination（人工受精）is increasing among lesbians.
Gay persons are in every kind of job.Some are very open about their homosexuality,and some are more private.Some______(53)their sexual orientation as a biological given and others as a choice.For those women who see it as a choice,one reason often given is the inequality in most heterosexual（异性恋的）relationships.
Homosexuality has been common in most cultures throughout history and generally______ (54).As a result,homosexual activity became a crime,______(55)which the penalty in early courts was death.Homosexual behavior is still______(56)in many countries and the United States.
Homosexuality later came to be viewed widely as less a sin than a sickness,but now no mentalhealth professional（具有专业资格的人）any longer ______ (57) homosexuality an illness. More recent theories to______(58)for homosexuality have included those based on biological and sociological factors.To date.______(59),there is no conclusive general theory that can explain the cause of homosexuality.
Attitudes______(60)homosexuality began to change in the second half of the 20th century. Gays attribute this,in part,to their own struggle for their rights and pride in their orientation. Some large companies now______(61)health-care benefits to the life partners of their gay employees. Many cities also have officially appointed lesbian and gay advisory（咨询的）committees.______(62)some attitudes have changed,however,prejudice（偏见）still exists,and in the late 1980s and early 1990s,there were considerable shouts against homosexuals,with attempt to ______(63)laws forbidding the granting of basic civil rights to gays.
The AIDS epidemic,which started in the 1980s,has devastated（毁坏）the gay community and brought it together as never before,The organized gay response to the lack of government financial support for fighting AIDS and to the needs of the thousands of AIDS victim______(64)they be gays or not,has been a model of community action.AIDS,however,has also______(65)people with another reason for their prejudice.
_________(61)
A:exclude
B:include
C:extend
D:intend
Homosexuals（同性恋者）
Many homosexuals prefer to be called gay or,for woman,lesbian.Most of them live quiet lives just______(51)anyone else.Some gay people have always raised children,______(52)or with partners,and the use of artificial insemination（人工受精）is increasing among lesbians.
Gay persons are in every kind of job.Some are very open about their homosexuality,and some are more private.Some______(53)their sexual orientation as a biological given and others as a choice.For those women who see it as a choice,one reason often given is the inequality in most heterosexual（异性恋的）relationships.
Homosexuality has been common in most cultures throughout history and generally______ (54).As a result,homosexual activity became a crime,______(55)which the penalty in early courts was death.Homosexual behavior is still______(56)in many countries and the United States.
Homosexuality later came to be viewed widely as less a sin than a sickness,but now no mentalhealth professional（具有专业资格的人）any longer ______ (57) homosexuality an illness. More recent theories to______(58)for homosexuality have included those based on biological and sociological factors.To date.______(59),there is no conclusive general theory that can explain the cause of homosexuality.
Attitudes______(60)homosexuality began to change in the second half of the 20th century. Gays attribute this,in part,to their own struggle for their rights and pride in their orientation. Some large companies now______(61)health-care benefits to the life partners of their gay employees. Many cities also have officially appointed lesbian and gay advisory（咨询的）committees.______(62)some attitudes have changed,however,prejudice（偏见）still exists,and in the late 1980s and early 1990s,there were considerable shouts against homosexuals,with attempt to ______(63)laws forbidding the granting of basic civil rights to gays.
The AIDS epidemic,which started in the 1980s,has devastated（毁坏）the gay community and brought it together as never before,The organized gay response to the lack of government financial support for fighting AIDS and to the needs of the thousands of AIDS victim______(64)they be gays or not,has been a model of community action.AIDS,however,has also______(65)people with another reason for their prejudice.
_________(61)
A:exclude
B:include
C:extend
D:intend
共用题干
Cell Phones
I Believe it or not,cell phones have been around for over a quarter of a century.The first commercial
cell phone systemfl was developed by the Japancoc in I 979.But cell phones have changed a lot
since that
time.The early cell phones were big and heavy but they have developed into small and light palm-sized mod-
els.There have been huge (lcveloprnents in their functions,too;we have had call forwarding,text messaging,
answering services and hands-free use for years,but now there are countless new facilities,su,ch as instant ac-
cess to the Internet and receiving and sending photos.
2 Cell phones have become very common in our lives;recent statistics suggest as many as one in three
people cii the planet now have a cell phone,and most of them say they couldn't live without one.Cell phones
are used in every area of our lives and have become a necessary tool,used for essential arrangements,social
contact and business.They have made it easier to call for help on the highway.They have made it possible to
keep in touch with people"on the move”一when people are traveling.
3 Cell phones have made communication easier and have reduced the need for family arguments.We
can use cell phones to let our family know we'11 be late or if there’。a sudden change of tian or an emergen-
cy.Cell phones have eased the worries of millions of parents when their teenagers are out late,they can now
contact their children at any time.
4 This does not mean that cell phones are all good news.They have brought with them a number of
new headaches for their owners;it costs a lot to replace stolen phones,something that is becoming a frequent
occurrence,and have you ever seen such huge phone bills? More serious,however,is the potential health
problem they bring:there are fears that radiation from the phones may cause brain tumor（肿瘤）.This may be
a time bomb waiting to happen to younger people who have grown up with cell phones that they simply can't
live without!
We can use cell phones to communicate with others when we encounter__________.
A:a necessity
B:an emergency
C:a number of new hcadaches
D:family arguments
F:big and light palm-sized models
F:countless new facilities
Cell Phones
I Believe it or not,cell phones have been around for over a quarter of a century.The first commercial
cell phone systemfl was developed by the Japancoc in I 979.But cell phones have changed a lot
since that
time.The early cell phones were big and heavy but they have developed into small and light palm-sized mod-
els.There have been huge (lcveloprnents in their functions,too;we have had call forwarding,text messaging,
answering services and hands-free use for years,but now there are countless new facilities,su,ch as instant ac-
cess to the Internet and receiving and sending photos.
2 Cell phones have become very common in our lives;recent statistics suggest as many as one in three
people cii the planet now have a cell phone,and most of them say they couldn't live without one.Cell phones
are used in every area of our lives and have become a necessary tool,used for essential arrangements,social
contact and business.They have made it easier to call for help on the highway.They have made it possible to
keep in touch with people"on the move”一when people are traveling.
3 Cell phones have made communication easier and have reduced the need for family arguments.We
can use cell phones to let our family know we'11 be late or if there’。a sudden change of tian or an emergen-
cy.Cell phones have eased the worries of millions of parents when their teenagers are out late,they can now
contact their children at any time.
4 This does not mean that cell phones are all good news.They have brought with them a number of
new headaches for their owners;it costs a lot to replace stolen phones,something that is becoming a frequent
occurrence,and have you ever seen such huge phone bills? More serious,however,is the potential health
problem they bring:there are fears that radiation from the phones may cause brain tumor（肿瘤）.This may be
a time bomb waiting to happen to younger people who have grown up with cell phones that they simply can't
live without!
We can use cell phones to communicate with others when we encounter__________.
A:a necessity
B:an emergency
C:a number of new hcadaches
D:family arguments
F:big and light palm-sized models
F:countless new facilities
共用题干
Where Did the Earth's Water Come From?
Earth is located within the"snow line"of the solar system,the region closest to the Sun where H2 0 is primarily in liquid or gaseous form,if at all.______(46)The snow line phenomena is reflected in the water content of planets like Mercury,Venus,and Mars. Water is absent on Mercury.On Venus,H2O only exists as a trace element in the atmosphere.Mars only has a thin veneer of ice in its polar regions.In general,water is rare within the snow line.
Why does Earth have so much water relative to the other inner planets?71%of the surface is covered in the oceans,more than half of which is deeper than 3,000 meters,with an approximate total volume of 1.3 billion cu km.______(47)
There are various theories as to where all the Earth's water came from,but several theories have fared better than the others.______(48)When the Earth was in the process of forming,with a radius just 40%smaller than at present,it would have had enough gravity to hold on to a tenuous atmosphere with water vapor. The first water vapor on the planet would have come from the planet's internals,where volatile(low weight)chemicals would have a tendency to float to the top,and heavy chemicals(iron and nickel)would sink.
Though the first of Earth's water came about through volcanism,this alone probably didn't produce enough to form stable pools on the surface.______(49)Comparing the isotope ratios of water on Earth and water from comets and asteroids has revealed that the majority of the Earth's water comes from asteroids.
Throughout its history,Earth's water has increased in volume due to biological processes. In the early seas of Earth,hydrogen sulfide would have been in great supply,which,when reacted with carbon dioxide from the atmosphere during photosynthesis in sulfide-reducing bacteria,would have produced hydrogen,sulfur,and water.______(50)
________（46）
A: More water was added to the planet during several hypothesized large impacts from asteroids from the outer asteroid belt.
B:We know that the oceans existed as early as 100 million years after the formation of the Earth.
C:Still,the oceans only make up 0.023%of the Earth's total mass.
D:Astronomers say Earth s water may have come from space.
E:The snow line is located in the outerasteroid belt,between the orbits of Mars and Jupiter.
F: Many geologists believe that the majority of Earth's water generated through this process.
Where Did the Earth's Water Come From?
Earth is located within the"snow line"of the solar system,the region closest to the Sun where H2 0 is primarily in liquid or gaseous form,if at all.______(46)The snow line phenomena is reflected in the water content of planets like Mercury,Venus,and Mars. Water is absent on Mercury.On Venus,H2O only exists as a trace element in the atmosphere.Mars only has a thin veneer of ice in its polar regions.In general,water is rare within the snow line.
Why does Earth have so much water relative to the other inner planets?71%of the surface is covered in the oceans,more than half of which is deeper than 3,000 meters,with an approximate total volume of 1.3 billion cu km.______(47)
There are various theories as to where all the Earth's water came from,but several theories have fared better than the others.______(48)When the Earth was in the process of forming,with a radius just 40%smaller than at present,it would have had enough gravity to hold on to a tenuous atmosphere with water vapor. The first water vapor on the planet would have come from the planet's internals,where volatile(low weight)chemicals would have a tendency to float to the top,and heavy chemicals(iron and nickel)would sink.
Though the first of Earth's water came about through volcanism,this alone probably didn't produce enough to form stable pools on the surface.______(49)Comparing the isotope ratios of water on Earth and water from comets and asteroids has revealed that the majority of the Earth's water comes from asteroids.
Throughout its history,Earth's water has increased in volume due to biological processes. In the early seas of Earth,hydrogen sulfide would have been in great supply,which,when reacted with carbon dioxide from the atmosphere during photosynthesis in sulfide-reducing bacteria,would have produced hydrogen,sulfur,and water.______(50)
________（46）
A: More water was added to the planet during several hypothesized large impacts from asteroids from the outer asteroid belt.
B:We know that the oceans existed as early as 100 million years after the formation of the Earth.
C:Still,the oceans only make up 0.023%of the Earth's total mass.
D:Astronomers say Earth s water may have come from space.
E:The snow line is located in the outerasteroid belt,between the orbits of Mars and Jupiter.
F: Many geologists believe that the majority of Earth's water generated through this process.
共用题干
第二篇
The American Industry
A history of long and effortless success can be a dreadful handicap,but if properly handled,it may become a driving force.When the United States entered just such a glowing period after the end of the Second World War,it had a market eight times larger than any competitor,giving its industries unparalleled economies of scale.Its scientists were the world's best,its workers the most skilled.America and Americans were prosperous beyond the dreams of the Europeans and Asians whose economies the war had destroyed.
It was inevitable that this primacy should have narrowed as other countries grew richer. Just as inevitably,the retreat from predominance proved painful.By the mid-1980s Americans had found themselves at a loss over their fading industrial competitiveness.Some huge American industries, such as consumer electronics,had shrunk or vanished in the face of foreign competition.By 1987 there was only one American television maker left,Zenith.(Now there is none:Zenith was bought by South Korea's LG Electronics in July.)Foreign-made cars and textiles were sweeping into the domestic market. America's machine-tool industry was on the ropes.For a while it looked as though the making of semiconductors,which America had which sat at the heart of the new computer age, was going to be the next casualty.
All of this caused a crisis of confidence.Americans stopped taking prosperity for granted.They began to believe that their way of doing business was failing,and that their incomes would therefore shortly begin to fall as well. The mid-1980s brought one inquiry after another into the causes of America's industrial decline.Their sometimes sensational findings were filled with warnings about the growing competition from overseas.
How things have changed!In 1995 the United States can look back on five years of solid growth while Japan has been struggling. Few Americans attribute this solely to such obvious causes as a devalued dollar or the turning of the business cycle.Self-doubt has yielded to blind pride."American industry has changed its structure,has gone on a diet,has learnt to be more quick-witted,"according to Richard Cavanagh,executive dean of Harvard's Kennedy School of Government,"It makes me proud to be an American just to see how our businesses are improving their productivity,"says Stephen Moore of the Cato Institute,a think-tank in Washington,DC.And William Sahlman of the Harvard Business School believes that people will look back on this period as"a golden age of business management in the United States."
What can be inferred from the passage?
A:It is human nature to shift between self-doubt and blind pride.
B:Intense competition may contribute to economic progress.
C:The revival of the economy depends on international cooperation.
D:A long history of success may pave the way for further development.
第二篇
The American Industry
A history of long and effortless success can be a dreadful handicap,but if properly handled,it may become a driving force.When the United States entered just such a glowing period after the end of the Second World War,it had a market eight times larger than any competitor,giving its industries unparalleled economies of scale.Its scientists were the world's best,its workers the most skilled.America and Americans were prosperous beyond the dreams of the Europeans and Asians whose economies the war had destroyed.
It was inevitable that this primacy should have narrowed as other countries grew richer. Just as inevitably,the retreat from predominance proved painful.By the mid-1980s Americans had found themselves at a loss over their fading industrial competitiveness.Some huge American industries, such as consumer electronics,had shrunk or vanished in the face of foreign competition.By 1987 there was only one American television maker left,Zenith.(Now there is none:Zenith was bought by South Korea's LG Electronics in July.)Foreign-made cars and textiles were sweeping into the domestic market. America's machine-tool industry was on the ropes.For a while it looked as though the making of semiconductors,which America had which sat at the heart of the new computer age, was going to be the next casualty.
All of this caused a crisis of confidence.Americans stopped taking prosperity for granted.They began to believe that their way of doing business was failing,and that their incomes would therefore shortly begin to fall as well. The mid-1980s brought one inquiry after another into the causes of America's industrial decline.Their sometimes sensational findings were filled with warnings about the growing competition from overseas.
How things have changed!In 1995 the United States can look back on five years of solid growth while Japan has been struggling. Few Americans attribute this solely to such obvious causes as a devalued dollar or the turning of the business cycle.Self-doubt has yielded to blind pride."American industry has changed its structure,has gone on a diet,has learnt to be more quick-witted,"according to Richard Cavanagh,executive dean of Harvard's Kennedy School of Government,"It makes me proud to be an American just to see how our businesses are improving their productivity,"says Stephen Moore of the Cato Institute,a think-tank in Washington,DC.And William Sahlman of the Harvard Business School believes that people will look back on this period as"a golden age of business management in the United States."
What can be inferred from the passage?
A:It is human nature to shift between self-doubt and blind pride.
B:Intense competition may contribute to economic progress.
C:The revival of the economy depends on international cooperation.
D:A long history of success may pave the way for further development.
He said some harshwords about his brother.
A: proper
B: normal
C: unkind
D: unclear
A: proper
B: normal
C: unkind
D: unclear
Our aim was to update the health service,and we succeeded.
A: modernize
B: offer
C: provide
D: fund
A: modernize
B: offer
C: provide
D: fund
共用题干
Vibrating Rubber Celiphones
Vibrating rubber celiphones could be the next big thing in mobile communications.They allow people to press the phone to transmit vibrations along with their______(51)words.According to a research team at the MIT Media Lab in Cambridge,Massachusetts,the idea will make______ (52)more fun.
Many mobile phones can already vibrate instead of ringing______(53)you do not want people to know you are getting a call. "But these______ (54) are too simple for subtle（敏感的） communication".______(55)Angela Chang of the lab's Tangible Media Group."They're either on or off,"she says.
But when you hold Chang's rubber cellphone your fingers and thumb wrap around five ______(56)speakers. They vibrate______(57)your skin around 250 times per second.Beneath these speakers sit pressure sensors（传感器）,so you can transmit vibration as well as ______(58)it. When you squeeze with a finger,a vibration signal is transmitted______(59) your caller's corresponding finger,its speed______(60)on how hard you squeeze.
Chang says that within a few minutes of being given the phones,students were using the vibration feature to______(61)emphasis to what they were saying. Over time,people even began to transmit their own kind of ad hoc（特别的）" Morse code " , which they would repeat back to show they were______(62)what the other person was saying.
Chang thinks"vibralanguages"could function for the same______(63)as texting:sometimes people want to communicate______(64)without everyone nearby knowing what they're saying."And______(65)actually being able to shake someone's hand when you close a business deal,"she says.
_________(60)
A:depends
B:bases
C:puts
D:focuses
Vibrating Rubber Celiphones
Vibrating rubber celiphones could be the next big thing in mobile communications.They allow people to press the phone to transmit vibrations along with their______(51)words.According to a research team at the MIT Media Lab in Cambridge,Massachusetts,the idea will make______ (52)more fun.
Many mobile phones can already vibrate instead of ringing______(53)you do not want people to know you are getting a call. "But these______ (54) are too simple for subtle（敏感的） communication".______(55)Angela Chang of the lab's Tangible Media Group."They're either on or off,"she says.
But when you hold Chang's rubber cellphone your fingers and thumb wrap around five ______(56)speakers. They vibrate______(57)your skin around 250 times per second.Beneath these speakers sit pressure sensors（传感器）,so you can transmit vibration as well as ______(58)it. When you squeeze with a finger,a vibration signal is transmitted______(59) your caller's corresponding finger,its speed______(60)on how hard you squeeze.
Chang says that within a few minutes of being given the phones,students were using the vibration feature to______(61)emphasis to what they were saying. Over time,people even began to transmit their own kind of ad hoc（特别的）" Morse code " , which they would repeat back to show they were______(62)what the other person was saying.
Chang thinks"vibralanguages"could function for the same______(63)as texting:sometimes people want to communicate______(64)without everyone nearby knowing what they're saying."And______(65)actually being able to shake someone's hand when you close a business deal,"she says.
_________(60)
A:depends
B:bases
C:puts
D:focuses