单选题—The water changes into thick ice covering rivers and lakes in winter in Harbin.—_____ in Urumqi and children go skating on it then.A So is itB So it doesC So it isD So does it

请阅读短文，完成此题。
When we analyze the salt salinity(盐溶度 ) of ocean waters, we find that it varies only slightly from place to place. Nevertheless, some of these small changes are important. There are three basic processes that cause a change in oceanic salinity. One of these is the subtraction of water from the ocean by means of evaporation. In this manner, the salinity is increased, since the salt stays behind. If this is carried to the extreme, of course, white salt would be left behind; this, by the way, is how much of the table salt we use is actually obtained.
The opposite of evaporation is precipitation, such as rain, by which water is added to the ocean. Here the ocean is being diluted so that the salinity is decreased. This may occur in areas of
high rainfall or in coastal regions where rivers flow into the ocean. Thus salinity may be increased by the subtraction of water by-evaporation, or decreased by the addition of fresh water by precipitation.
Normally, in hot regions where the sun is very strong, the ocean salinity is somewhat higher than it is in other parts of the world where there is not as much evaporation. Similarly, in coastal regions where rivers dilute the sea, salinity is somewhat lower than in other oceanic areas.
A third process by which salinity may be altered is associated with the formation and melting of sea ice. When seawater is frozen, the dissolved materials are left behind. In this manner, seawater directly beneath freshly formed sea ice has a higher salinity than it did before the ice appeared. Of course, when this ice melts, it will tend to decrease the salinity of the surrounding water.
In the Weddell Sea, the densest water in the ocean is formed as a result of this freezing process, which increases the salinity of cold water. This heavy water sinks and is found in the deeper portion of the oceans of the world.

The purpose of mentioning the Weddell Sea is__________.
查看材料

A．to give an example of cold-water salinity
B．to point out the location of deep waters
C．to make a comparison between hot-water salinity and cold-water salinity
D．to show that the water in the Weddell Sea varies in salinity from place to place

请阅读短文，完成此题。
When we analyze the salt salinity(盐溶度 ) of ocean waters, we find that it varies only slightly from place to place. Nevertheless, some of these small changes are important. There are three basic processes that cause a change in oceanic salinity. One of these is the subtraction of water from the ocean by means of evaporation. In this manner, the salinity is increased, since the salt stays behind. If this is carried to the extreme, of course, white salt would be left behind; this, by the way, is how much of the table salt we use is actually obtained.
The opposite of evaporation is precipitation, such as rain, by which water is added to the ocean. Here the ocean is being diluted so that the salinity is decreased. This may occur in areas of
high rainfall or in coastal regions where rivers flow into the ocean. Thus salinity may be increased by the subtraction of water by-evaporation, or decreased by the addition of fresh water by precipitation.
Normally, in hot regions where the sun is very strong, the ocean salinity is somewhat higher than it is in other parts of the world where there is not as much evaporation. Similarly, in coastal regions where rivers dilute the sea, salinity is somewhat lower than in other oceanic areas.
A third process by which salinity may be altered is associated with the formation and melting of sea ice. When seawater is frozen, the dissolved materials are left behind. In this manner, seawater directly beneath freshly formed sea ice has a higher salinity than it did before the ice appeared. Of course, when this ice melts, it will tend to decrease the salinity of the surrounding water.
In the Weddell Sea, the densest water in the ocean is formed as a result of this freezing process, which increases the salinity of cold water. This heavy water sinks and is found in the deeper portion of the oceans of the world.

It can be known from the passage that increase in the salinity of ocean water is caused by__________.
查看材料

A．melting of sea ice
B．precipitation
C．evaporation
D．supplement of salt

请阅读短文，完成此题。
When we analyze the salt salinity(盐溶度 ) of ocean waters, we find that it varies only slightly from place to place. Nevertheless, some of these small changes are important. There are three basic processes that cause a change in oceanic salinity. One of these is the subtraction of water from the ocean by means of evaporation. In this manner, the salinity is increased, since the salt stays behind. If this is carried to the extreme, of course, white salt would be left behind; this, by the way, is how much of the table salt we use is actually obtained.
The opposite of evaporation is precipitation, such as rain, by which water is added to the ocean. Here the ocean is being diluted so that the salinity is decreased. This may occur in areas of
high rainfall or in coastal regions where rivers flow into the ocean. Thus salinity may be increased by the subtraction of water by-evaporation, or decreased by the addition of fresh water by precipitation.
Normally, in hot regions where the sun is very strong, the ocean salinity is somewhat higher than it is in other parts of the world where there is not as much evaporation. Similarly, in coastal regions where rivers dilute the sea, salinity is somewhat lower than in other oceanic areas.
A third process by which salinity may be altered is associated with the formation and melting of sea ice. When seawater is frozen, the dissolved materials are left behind. In this manner, seawater directly beneath freshly formed sea ice has a higher salinity than it did before the ice appeared. Of course, when this ice melts, it will tend to decrease the salinity of the surrounding water.
In the Weddell Sea, the densest water in the ocean is formed as a result of this freezing process, which increases the salinity of cold water. This heavy water sinks and is found in the deeper portion of the oceans of the world.

This passage mainly tells us about__________.
查看材料

A．the analysis of the salinity of ocean waters
B．the causes of the variation in oceanic salinity
C．the importance of the changes in oceanic salinity
D．the different forms of salts in ocean waters

共用题干
第三篇

Preserve the Environment

Throughout history man has changed his physical environment in order to improve his way of life.
With the tools of technology he has altered many physical features of the earth.He has transformed
woodlands into farmland,and made lakes and reservoirs out of rivers for irrigation purposes or hydroelectric
power. Man has also modified the face of the earth by draining marshes and cutting through mountains to
build roads and railways.
However,man's changes to the physical environment have not always had beneficial results.Today,
pollution of the air and water is an increasing danger to the health of the planet.Each day thousands of tons
of gases come out of the exhausts of motor vehicles;smoke from factories pollutes the air of industrialized areas
and the surrounding areas of countryside.The air in cities is becoming increasingly unhealthy.
The pollution of water is equally harmful.In the sea,pollution from oil is increasing and is killing enor-
mous numbers of algae（水藻）,fish and birds.The whole ecological balance of the sea is being changed.
The same problem exists in rivers.Industrial wastes have already made many rivers lifeless.
Conservationists believe that it is now necessary for man to limit the growth of technology in order to sur-
vive on earth.

According to the passage,pollution of the air and water is caused by__________.
A:thousands of tons of gases coming out of the exhausts of motor vehicles
B:the changes of the environment that technology has brought to man
C:the increasing amount of oil that has been produced
D:industrial wastes discharged into rivers

When the glaciers（ ）after the last ice age,the five Great Lakes of North America were formed.

A.advanced
B.evaporated
C.thawed
D.exploded

共用题干
Water

Earth is like a big blue marble.From high above the Earth and from the moon,the planet gleams and shines.The blue water in the oceans and seas of the Earth makes a dramatic image.The white clouds above the Earth add beauty to the picture.Water is the source of this beauty and the source of life on Earth.It is the reason people can live on this planet. Water is everywhere.(46)_______.It is in the soil,the ground that grows the food.Water is in rock deep under the ground, in natural holding areas一in storage.In a real sense,water keeps Earth alive.
Nature has an unchanging amount of water. Nature has a perfect system for recycling water. (47)_____.It falls as rain.Then it goes to one of three places.It might sink slowly through the soil into the natural holding areas in the rock.(48)_______一by becoming vapor,or gas.It might run off into streams,rivers and oceans.By itself,nature can keep the balance and provide plenty of clean water for us.Nature recycles water.
However,people cause problems for this natural recycling system.Nature's recycling system can work well(49)________.Some ways that people upset nature are easy to understand.For example, dirty sewage（污水沟系统）water from homes and factories must not mix with drinking water. People get sick from drinking contaminated water. Sometimes water from factories goes into streams and rivers.It enters into the groundwater. It can flow into lakes too.This kind of contamination from industry(waste water from factories) can be dangerous for people.If water contains poisons and chemicals,it is poison.(50)________;some poisons kill people as well as birds and animals.Without knowing,people can upset nature's recycling system.
Lakes and rivers add beauty to the world. People enjoy water for entertainment purposes,too. People enjoy swimming and playing in the cool water of a lake in the summer. They like to ride on boats on rivers.Many people enjoy catching fish in the rivers.They fish for food and for sport.However,in some places,the water of the lakes and rivers is no longer safe.These rivers and lakes are contaminated.The fish are dying because of the chemicals from farms and factories.People cannot swim in the polluted water.

_________（49）
A:Poison makes people sick
B:It is in the air that people breathe
C:We can not live without water
D:Water is used again and again
E:only if people work with the system and not against it
F: It might disappear into the air quickly

共用题干
Europa's Watery Underworld

Europa,one of Jupiter's 63 known moons,looks bright and icy on the surface.But appearances can be
deceiving:Miles within its cracked,frigid shell,Europa probably hides giant pools of liquid water. Where
scientists find liquid water,they hope to find life as well.
Since we can't go diving into Europa's depths just yet,scientists instead have to investigate the moon's
surface for clues to what lies beneath.In a new study,scientists investigated one group of strange ice patterns
on Europa and concluded that the formations mark the top of an underground pool that holds as much water
as the U.S.Great Lakes.
Pictures of Europa,which is slightly smaller than Earth's moon,clearly show a tangled,icy mishmash
of lines and cracks known as"chaos terrains".These chaotic places cover more than half of Europa. For
more than 10 years,scientists have wondered what causes the formations.The new study suggests that they
arise from the mixing of vast underground stores of liquid water with icy material near the surface.
For scientists who suspect that Europa also may be hiding life beneath its icy surface,the news about
the new lake is exciting.
"It would be great if these lakes harbored life,"Britney Schmidt,a planetary scientist who worked on
the study,told Science News."But even if they didn't,they say that Europa is doing something interesting
and active right now."
Schmidt,a scientist at the University of Texas at Austin,and her colleagues wanted to know how chaos
terrains form.Since they couldn't rocket to Europa to see for themselves,they searched for similar forma-
tions here on Earth.They studied collapsed ice shelves in Antarctica and icy caps on volcanoes in Iceland.
Those features on Earth formed when liquid water mixed with ice.The scientists now suspect something
similar might be happening on Europa:that as water and ice of different temperatures mingle and shift,the
surface fractures.This would explain the jumbled ice sculptures.
"Fracturing catastrophically disrupts the ice in the same way that it causes ice shelves to collapse on
Earth,"Schmidt told Science News.She and her team found that the process could be causing chaos terrains
to form quickly on Europa.
The new study suggests that on this moon,elements such as oxygen from the surface blend with the
deep bodies of water. That mixture may create an environment that supports life.

The strange ice patterns on Europa are formed as a result of a mixture of liquid water and solid material underground water pool.
A:Right
B:Wrong
C:Not mentioned

共用题干
第一篇

Water Resources on the Earth

The second most important constituent（构成成分）of the biosphere（生物圈）is liquid water. This can only exist in a very narrow range of temperatures,since water freezes at 0℃and boils a 100℃．Life as we know it would only be possible on the surface of a planet which had temperature: somewhere within this narrow range.
The earth's supply of water probably remains fairly constant in quantity.The total quantity of water is not known very accurately,but it is about enough to cover the surface of the globe to a depth of about two and three-quarter kilometers.Most of it is in the form of the salt water of the oceans一about 97 percent. The rest is fresh.But three-quarters of this is in the form of ice at the poles and or mountains and cannot be used by living systems until melted.Of the remaining fraction,which h somewhat less than one percent of the whole.There is 10—20 times as much stored underground water as there is actually on the surface.There is also a tiny,but extremely important fraction of the water supply which is present as water vapour in the atmosphere.
Water vapour in the atmosphere is the channel through which the whole water circulation（循环） of the biosphere has to pass.Water evaporated（蒸发）from the surface of the oceans,from lakes and rivers and from moist（潮湿的）earth is added to it. From it the water comes out again as rain or snow,falling on either the sea or the land. There is,as might be expected, a more intensive evaporation per unit area over the sea and oceans than over the land,but there is more rainfall over the land than over the oceans and the balance is restored by the run off from the land in the form of rivers.

The word"fraction"in the second paragraph means________.
A:a large area
B:a very small amount
C:an important system
D:a major source of information

共用题干
第一篇

Water Resources on the Earth

The second most important constituent（构成成分）of the biosphere（生物圈）is liquid water. This can only exist in a very narrow range of temperatures,since water freezes at 0℃and boils a 100℃．Life as we know it would only be possible on the surface of a planet which had temperature: somewhere within this narrow range.
The earth's supply of water probably remains fairly constant in quantity.The total quantity of water is not known very accurately,but it is about enough to cover the surface of the globe to a depth of about two and three-quarter kilometers.Most of it is in the form of the salt water of the oceans一about 97 percent. The rest is fresh.But three-quarters of this is in the form of ice at the poles and or mountains and cannot be used by living systems until melted.Of the remaining fraction,which h somewhat less than one percent of the whole.There is 10—20 times as much stored underground water as there is actually on the surface.There is also a tiny,but extremely important fraction of the water supply which is present as water vapour in the atmosphere.
Water vapour in the atmosphere is the channel through which the whole water circulation（循环） of the biosphere has to pass.Water evaporated（蒸发）from the surface of the oceans,from lakes and rivers and from moist（潮湿的）earth is added to it. From it the water comes out again as rain or snow,falling on either the sea or the land. There is,as might be expected, a more intensive evaporation per unit area over the sea and oceans than over the land,but there is more rainfall over the land than over the oceans and the balance is restored by the run off from the land in the form of rivers.

Liquid water only exists________.
A: in the center of the earth
B:on the surface of our planet
C:in the coastal areas of the earth
D:in a very narrow range of temperatures

The ice is not thick enough to bear the weight of a tank.

A:suffer
B:accept
C:receive
D:support

请阅读短文，完成此题。
When we analyze the salt salinity(盐溶度 ) of ocean waters, we find that it varies only slightly from place to place. Nevertheless, some of these small changes are important. There are three basic processes that cause a change in oceanic salinity. One of these is the subtraction of water from the ocean by means of evaporation. In this manner, the salinity is increased, since the salt stays behind. If this is carried to the extreme, of course, white salt would be left behind; this, by the way, is how much of the table salt we use is actually obtained.
The opposite of evaporation is precipitation, such as rain, by which water is added to the ocean. Here the ocean is being diluted so that the salinity is decreased. This may occur in areas of
high rainfall or in coastal regions where rivers flow into the ocean. Thus salinity may be increased by the subtraction of water by-evaporation, or decreased by the addition of fresh water by precipitation.
Normally, in hot regions where the sun is very strong, the ocean salinity is somewhat higher than it is in other parts of the world where there is not as much evaporation. Similarly, in coastal regions where rivers dilute the sea, salinity is somewhat lower than in other oceanic areas.
A third process by which salinity may be altered is associated with the formation and melting of sea ice. When seawater is frozen, the dissolved materials are left behind. In this manner, seawater directly beneath freshly formed sea ice has a higher salinity than it did before the ice appeared. Of course, when this ice melts, it will tend to decrease the salinity of the surrounding water.
In the Weddell Sea, the densest water in the ocean is formed as a result of this freezing process, which increases the salinity of cold water. This heavy water sinks and is found in the deeper portion of the oceans of the world.

Which of the following is not the cause of the decrease in the oceanic salinity?
查看材料

A．Precipitation.
B．Rain and snow.
C．Formation of ice.
D．Addition of water by rivers.

请阅读短文，完成此题。
When we analyze the salt salinity(盐溶度 ) of ocean waters, we find that it varies only slightly from place to place. Nevertheless, some of these small changes are important. There are three basic processes that cause a change in oceanic salinity. One of these is the subtraction of water from the ocean by means of evaporation. In this manner, the salinity is increased, since the salt stays behind. If this is carried to the extreme, of course, white salt would be left behind; this, by the way, is how much of the table salt we use is actually obtained.
The opposite of evaporation is precipitation, such as rain, by which water is added to the ocean. Here the ocean is being diluted so that the salinity is decreased. This may occur in areas of
high rainfall or in coastal regions where rivers flow into the ocean. Thus salinity may be increased by the subtraction of water by-evaporation, or decreased by the addition of fresh water by precipitation.
Normally, in hot regions where the sun is very strong, the ocean salinity is somewhat higher than it is in other parts of the world where there is not as much evaporation. Similarly, in coastal regions where rivers dilute the sea, salinity is somewhat lower than in other oceanic areas.
A third process by which salinity may be altered is associated with the formation and melting of sea ice. When seawater is frozen, the dissolved materials are left behind. In this manner, seawater directly beneath freshly formed sea ice has a higher salinity than it did before the ice appeared. Of course, when this ice melts, it will tend to decrease the salinity of the surrounding water.
In the Weddell Sea, the densest water in the ocean is formed as a result of this freezing process, which increases the salinity of cold water. This heavy water sinks and is found in the deeper portion of the oceans of the world.

Which of the following statements is TRUE according to the passage?
查看材料

A．Oceanic salinity has great effect on sea life.
B．Many factors combine to cause changes in oceanic salinity.
C．The movement of the water is related to the amount of salt.
D．The temperature of the water has much to do with the oceanic salinity.

共用题干
第三篇

Preserve the Environment

Throughout history man has changed his physical environment in order to improve his way of life.
With the tools of technology he has altered many physical features of the earth.He has transformed
woodlands into farmland,and made lakes and reservoirs out of rivers for irrigation purposes or hydroelectric
power. Man has also modified the face of the earth by draining marshes and cutting through mountains to
build roads and railways.
However,man's changes to the physical environment have not always had beneficial results.Today,
pollution of the air and water is an increasing danger to the health of the planet.Each day thousands of tons
of gases come out of the exhausts of motor vehicles;smoke from factories pollutes the air of industrialized areas
and the surrounding areas of countryside.The air in cities is becoming increasingly unhealthy.
The pollution of water is equally harmful.In the sea,pollution from oil is increasing and is killing enor-
mous numbers of algae（水藻）,fish and birds.The whole ecological balance of the sea is being changed.
The same problem exists in rivers.Industrial wastes have already made many rivers lifeless.
Conservationists believe that it is now necessary for man to limit the growth of technology in order to sur-
vive on earth.

Who would most probably disagree with conservationists?
A:Industrialists.
B:Ecologists.
C:Businessmen.
D:Environmentalists.

The ice is not thick enough to bear the weight of a tank.

A:suffer
B:accept
C:receive
D:support

根据下列内容，回答201-205题。
When we analyze the salt salinity(盐浓度) of ocean waters, we find that it varies only slightlyfrom place to place. Nevertheless, some of these small changes are important. There are three basicprocesses that cause a change in oceanic salinity. One of these is the subtraction of water from theocean by means of evaporation. In this manner, the salinity is increased, since the salt stays be-hind. If this is carried to the extreme, of course, white salt would be left behind; this, by the
way, is how much of the table salt we use is actually obtained.
The opposite of evaporation is precipitation, such as rain, by which water is added to theocean. Here the ocean is being diluted so that the salinity is decreased. This may occur in areas ofhigh rainfall or in coastal regions where rivers flow into the ocean. Thus salinity may be increasedby the subtraction of water by evaporation, or decreased by the addition of fresh water by precipi-tation.
Normally, in hot regions where the sun is very strong, the ocean salinity is somewhat higherthan it is in other parts of the world where there is not as much evaporation. Similarly, in coastalregions where rivers dilute the sea, salinity is somewhat lower than in other oceanic areas.
A third process by which salinity may be altered is associated with the formation and melting ofsea ice. When seawater is frozen, the dissolved materials are left behind. In thismanner, seawaterdirectly beneath freshly formed sea ice has a higher salinity than it did before the ice appeared.
Of course, when this ice melts, it will tend to decrease the salinity of the surrounding water.
In the Weddell Sea, the densest water in the ocean is formed as a result of this freezing pro-cess, which increases the salinity of cold water. This heavy water sinks and is found in the deeperportion of the oceans of the world.
This passage mainly tells us about___________.

A.the analysis of the salinity of ocean waters
B.the causes of the variation in oceanic salinity
C.the importance of the changes in oceanic salinity
D.the different forms of salts in ocean waters

共用题干
Europa's Watery Underworld

Europa,one of Jupiter's 63 known moons,looks bright and icy on the surface.But appearances can be
deceiving:Miles within its cracked,frigid shell,Europa probably hides giant pools of liquid water. Where
scientists find liquid water,they hope to find life as well.
Since we can't go diving into Europa's depths just yet,scientists instead have to investigate the moon's
surface for clues to what lies beneath.In a new study,scientists investigated one group of strange ice patterns
on Europa and concluded that the formations mark the top of an underground pool that holds as much water
as the U.S.Great Lakes.
Pictures of Europa,which is slightly smaller than Earth's moon,clearly show a tangled,icy mishmash
of lines and cracks known as"chaos terrains".These chaotic places cover more than half of Europa. For
more than 10 years,scientists have wondered what causes the formations.The new study suggests that they
arise from the mixing of vast underground stores of liquid water with icy material near the surface.
For scientists who suspect that Europa also may be hiding life beneath its icy surface,the news about
the new lake is exciting.
"It would be great if these lakes harbored life,"Britney Schmidt,a planetary scientist who worked on
the study,told Science News."But even if they didn't,they say that Europa is doing something interesting
and active right now."
Schmidt,a scientist at the University of Texas at Austin,and her colleagues wanted to know how chaos
terrains form.Since they couldn't rocket to Europa to see for themselves,they searched for similar forma-
tions here on Earth.They studied collapsed ice shelves in Antarctica and icy caps on volcanoes in Iceland.
Those features on Earth formed when liquid water mixed with ice.The scientists now suspect something
similar might be happening on Europa:that as water and ice of different temperatures mingle and shift,the
surface fractures.This would explain the jumbled ice sculptures.
"Fracturing catastrophically disrupts the ice in the same way that it causes ice shelves to collapse on
Earth,"Schmidt told Science News.She and her team found that the process could be causing chaos terrains
to form quickly on Europa.
The new study suggests that on this moon,elements such as oxygen from the surface blend with the
deep bodies of water. That mixture may create an environment that supports life.

The liquid water of an underground pool of Europa is estimated as much as the volume of the U.S.Great Lakes.
A:Right
B:Wrong
C:Not mentioned

共用题干
Europa's Watery Underworld

Europa,one of Jupiter's 63 known moons,looks bright and icy on the surface.But appearances can be
deceiving:Miles within its cracked,frigid shell,Europa probably hides giant pools of liquid water. Where
scientists find liquid water,they hope to find life as well.
Since we can't go diving into Europa's depths just yet,scientists instead have to investigate the moon's
surface for clues to what lies beneath.In a new study,scientists investigated one group of strange ice patterns
on Europa and concluded that the formations mark the top of an underground pool that holds as much water
as the U.S.Great Lakes.
Pictures of Europa,which is slightly smaller than Earth's moon,clearly show a tangled,icy mishmash
of lines and cracks known as"chaos terrains".These chaotic places cover more than half of Europa. For
more than 10 years,scientists have wondered what causes the formations.The new study suggests that they
arise from the mixing of vast underground stores of liquid water with icy material near the surface.
For scientists who suspect that Europa also may be hiding life beneath its icy surface,the news about
the new lake is exciting.
"It would be great if these lakes harbored life,"Britney Schmidt,a planetary scientist who worked on
the study,told Science News."But even if they didn't,they say that Europa is doing something interesting
and active right now."
Schmidt,a scientist at the University of Texas at Austin,and her colleagues wanted to know how chaos
terrains form.Since they couldn't rocket to Europa to see for themselves,they searched for similar forma-
tions here on Earth.They studied collapsed ice shelves in Antarctica and icy caps on volcanoes in Iceland.
Those features on Earth formed when liquid water mixed with ice.The scientists now suspect something
similar might be happening on Europa:that as water and ice of different temperatures mingle and shift,the
surface fractures.This would explain the jumbled ice sculptures.
"Fracturing catastrophically disrupts the ice in the same way that it causes ice shelves to collapse on
Earth,"Schmidt told Science News.She and her team found that the process could be causing chaos terrains
to form quickly on Europa.
The new study suggests that on this moon,elements such as oxygen from the surface blend with the
deep bodies of water. That mixture may create an environment that supports life.

The existence of liquid water is a necessity for a life-support environment.
A:Right
B:Wrong
C:Not mentioned

共用题干
第一篇

Water Resources on the Earth

The second most important constituent（构成成分）of the biosphere（生物圈）is liquid water. This can only exist in a very narrow range of temperatures,since water freezes at 0℃and boils a 100℃．Life as we know it would only be possible on the surface of a planet which had temperature: somewhere within this narrow range.
The earth's supply of water probably remains fairly constant in quantity.The total quantity of water is not known very accurately,but it is about enough to cover the surface of the globe to a depth of about two and three-quarter kilometers.Most of it is in the form of the salt water of the oceans一about 97 percent. The rest is fresh.But three-quarters of this is in the form of ice at the poles and or mountains and cannot be used by living systems until melted.Of the remaining fraction,which h somewhat less than one percent of the whole.There is 10—20 times as much stored underground water as there is actually on the surface.There is also a tiny,but extremely important fraction of the water supply which is present as water vapour in the atmosphere.
Water vapour in the atmosphere is the channel through which the whole water circulation（循环） of the biosphere has to pass.Water evaporated（蒸发）from the surface of the oceans,from lakes and rivers and from moist（潮湿的）earth is added to it. From it the water comes out again as rain or snow,falling on either the sea or the land. There is,as might be expected, a more intensive evaporation per unit area over the sea and oceans than over the land,but there is more rainfall over the land than over the oceans and the balance is restored by the run off from the land in the form of rivers.

Most of the fresh water on Earth________.
A:is in the form of ice at the poles and on mountains
B:is stored underground
C:is found in rivers and lakes
D:comes from the rain

共用题干
第一篇

Water Resources on the Earth

The second most important constituent（构成成分）of the biosphere（生物圈）is liquid water. This can only exist in a very narrow range of temperatures,since water freezes at 0℃and boils a 100℃．Life as we know it would only be possible on the surface of a planet which had temperature: somewhere within this narrow range.
The earth's supply of water probably remains fairly constant in quantity.The total quantity of water is not known very accurately,but it is about enough to cover the surface of the globe to a depth of about two and three-quarter kilometers.Most of it is in the form of the salt water of the oceans一about 97 percent. The rest is fresh.But three-quarters of this is in the form of ice at the poles and or mountains and cannot be used by living systems until melted.Of the remaining fraction,which h somewhat less than one percent of the whole.There is 10—20 times as much stored underground water as there is actually on the surface.There is also a tiny,but extremely important fraction of the water supply which is present as water vapour in the atmosphere.
Water vapour in the atmosphere is the channel through which the whole water circulation（循环） of the biosphere has to pass.Water evaporated（蒸发）from the surface of the oceans,from lakes and rivers and from moist（潮湿的）earth is added to it. From it the water comes out again as rain or snow,falling on either the sea or the land. There is,as might be expected, a more intensive evaporation per unit area over the sea and oceans than over the land,but there is more rainfall over the land than over the oceans and the balance is restored by the run off from the land in the form of rivers.

There is more of rainfall________.
A:over the mountains than over the rivers
B:over the rivers than over the mountains
C:over the land than over the oceans
D:over the oceans than over the land

共用题干
第一篇

Arctic Melt

Earth’s North and South Poles are famous for being cold and icy.Last year,however,the amnount of ice
in the Arctic Ocean（北冰洋）fell to a record low.
Normally,ice builds in Arctic waters around the North Pole each winter and shrinks（缩小）during the
summer. But for many years,the amount of ice left by the end of summer has been declining.
Since 1979,each decade has seen an 11.4 percent drop in end?of-summer ice cover. Between 1981 and
2000,ice in the Arctic lost 22 percent of its thickness,becoming I.13 meters thinner.
Last summer,Arctic sea ice reached its thinnest levels yet.By the end of summer 2007,the ice had
shrunk to cover just 4.2 million square kilometers.That's 38 percent less area than the average cover at that
time of year. And it's a very large 23 percent below the previous record low,which was set just 2 years ago.
This continuing trend has made scientists concerned.
There may be several reasons for the ice melt, says Jinlun Zhang, an oceanographer（海洋学家）at the
University of Washington at Seattle.Unusually strong winds blew through the Arctic last summer. The winds
pushed much of the ice out of the central Arctic,leaving a large area of thin ice and open water.
Scientists also suspect that fewer clouds cover the Arctic now than in the past.Clearer skies allow more
sunlight to reach the ocean.The extra heat warms both the water and the atmosphere.In parts of the Arctic
Ocean last year,surface temperatures were 3.5℃warmer than average and 1.5℃warmer than the previous
record high.
With both air and water getting warmer,the ice is melting from both above and below. In some parts of
the Beaufort Sea,north of Alaska and western Canada,ice that measured 3.3 meters thick at the beginning
of the summer measured just 50 centimeters by season's end.
The new measurements suggest that melting is far more severe than scientists have seen by just looking
at ice covcrfrom above,says Donald K. Perovich,a geophysicist at the U.S.Army Cold Regions Research
and Engineering Laboratory in Hanover,N.H.
Some scientists fear that the Arctic is stuck in a warming trend from which it may never recover.

The Beaufort Sea mentioned in Paragraph 7 is an example to show_________.
A:how acetirate the new measurements are
B:how thick the ice is in it
C:how serious the problem of the ice melt in the Arctic is
D:how dangerous it is to travel to it