D

　　In the atmosphere,carbon dioxide actd rather like a one-way mirror or the glass in the roof of a greenhouse which allows the sun's rays to enter but prevents the heat from excaping.

　　According to a weather expert's prediction,the atmosphere will be 3 warmer in the year 2050 than it is today, if man continues to burn luels at the present rate. If this warming up took place,the ice caps in the poles would begin to melt,thus raising sea level several meters and severely flooding coastal cities.Also，the increase in atmospheric temperature would lead to great changes in the climate of the northern hemisphere(半球),psooicbly resulting in an alteration of earth's chief food growing zones.

　　In the past,concern about a man - made warming of the earth has concentrated on the Arctic because the Antarctic is much colder and has a much thicker ice sheet.But the weather experts are now paying more attention to West Antarctic,which may be affected by a warming on the scale that will possibly take place in the next fifty years from on burning of fuels.

　　Satellite pictures showthat large areas of Antarctic ice are already disappearing.The evidence available suggests that a warming has taken place.This fits the theory that carbon dioxide warms the earth.

　　However,most of the fuel is burnt in the northern hemisphere,where temperatures seem to be falling.Scientists conclude,therefore,that up to now natural influences on the weather have exceeded those caused by man.The question is:Which natural cause has most effect on the weather?

　　One possibility is the variable behavior of the sun.Astronomers at one research station have studied the hot spots and cold spots(that is,the relatively less hot spots) on the sun. As the sun rotates(旋转),every 27.5 days,it presents hotter or colder faces to the earth,and different aspects to different parts of the earth.This seems to have a considerable effect on the distribution of the earth's atmospheric pressure,and consequently on wind circulation.The sun is also variable over a long term:its heat output goes up and down in cycles,the latest trend being downward.

　　Scientists are now finding mutual relations between models of solar weather interactions and the actual climate over many thousands of years ,including the last Ice Age.The problem is that the models are predicting that the world should be entering a new Ice Age and it is not.

　　One way of solving this theoretical difficulty is to assume a delay of thousands of years while the solar effects overcome the inertia(不活动，惰性) of the earth's climate.If this is right,the warming effect of carbon dioxide might thus be serving as a useful counter balance to the sun's diminishing heat.

　　68.It can be concluded that a concentration of carbon dioxide in the atmosphere would ___.

　　　A.mean a warming - up im the Arctic

　　　B.raise the temperature of the earth's surface

　　　C.prevent the sun's rays from reaching the earth's surface

　　　D.account for great changes in the climate in the northern hemiphere

　　69.Although the fuel consumption is greater in the northern hemisphere,temperatures there seem to be falling.This is _______.

　　　A.mainly because the levels of carbon dioxide are rising

　　　B.partly due to variations in the output of solar energy

　　　C.possibly because the ice caps in the poles are melting

　　　D.exclusively due to the effect of the inertia of the earth's climate

　　70.On the basis of their models,scientists are of the opinion that ________.

　　　A.the climate of the world should be becoming cooler

　　　B.the new Ice Age will be delayed by the greenhouse effect

　　　C.the man - made warming effect helps to increase the solar effects

　　　D.it will take thousands of years for the inertia of the earth's climate to take effect

Thousands of villages in the developing world have no telephones. They have no money to build telephone systems. A new kind of technology may help change this situation. I t reduces the cost of building and using telephone systems.

Traditional systems use wires to carry electrical signals from one telephone to another. The wires often cost much more than telephones. The new system is based on radio communication. Each telephone sends and receives signals through the air, but not through the wires. This reduces the cost greatly. The radio telephone gets their power from the sun.

Each is connected to a solar equipment that changes the sun’s energy into electricity. A battery stores the electricity until someone needs to make or receive a call. The telephone turns off by itself if the level of power in the battery falls too low. This prevents damage to the system. Each radio telephone is connected to a computer microprocessor. It rewards how many calls are sent and received. It controls the power supply.

The technology needs more study, but its new use of radio equipment sun power and computers may help start telephone ringing in the other parts of the world.

68. The radio telephone gets their power from_____.

A. the sun 　　　B. electricity 　　　C. battery 　　　D. a special equipment

69. Each telephone is connected to_____.

A. a solar equipment 　　　　　　　B. a radio machine

C. a computer microprocessor 　　　D. Both A and C

70. From the passage we can infer that_____.

A. the new telephone system costs less than before

B. we can not use the radio as before

C. the new telephone system will take the place of the old one

D. it will be much easier to radio from now on

71. The main idea of the passage is_____.

A. a simple telephone system has been invented and costs less money

B. thousands of villages will use the new telephone system very soon

C. traditional telephone system will become useless

D. the new system will be too good to use

Thousands of villages in the developing world have no telephones. They have no money to build telephone systems. A new kind of technology may help change this situation. I t reduces the cost of building and using telephone systems.
Traditional systems use wires to carry electrical signals from one telephone to another. The wires often cost much more than telephones. The new system is based on radio communication. Each telephone sends and receives signals through the air, but not through the wires. This reduces the cost greatly. The radio telephone gets their power from the sun.
Each is connected to a solar equipment that changes the sun’s energy into electricity. A battery stores the electricity until someone needs to make or receive a call. The telephone turns off by itself if the level of power in the battery falls too low. This prevents damage to the system. Each radio telephone is connected to a computer microprocessor. It rewards how many calls are sent and received. It controls the power supply.
The technology needs more study, but its new use of radio equipment sun power and computers may help start telephone ringing in the other parts of the world.
68. The radio telephone gets their power from_____.
A. the sun 　　　B. electricity 　　　C. battery 　　　D. a special equipment
69. Each telephone is connected to_____.
A. a solar equipment 　　　　　　　B. a radio machine
C. a computer microprocessor 　　　D. Both A and C
70. From the passage we can infer that_____.
A. the new telephone system costs less than before
B. we can not use the radio as before
C. the new telephone system will take the place of the old one
D. it will be much easier to radio from now on
71. The main idea of the passage is_____.
A. a simple telephone system has been invented and costs less money
B. thousands of villages will use the new telephone system very soon
C. traditional telephone system will become useless
D. the new system will be too good to use

In the atmosphere, carbon dioxide acts rather like a one-way mirror or the glass in the roof of a greenhouse which allows the sun's rays to enter but prevents the heat from escaping.

　　 According to a weather expert' s prediction, the atmosphere will be 3℃ warmer in the year 2050 than it is today, if man continues to burn fuels at the present rate. If this warming up took place, the ice caps in the poles would begin to melt, thus raising sea level several metres and severely flooding coastal cities. Also, the increase in atmospheric temperature would lead to great changes in the climate of the northern hemisphere (北半球), possibly resulting in an alteration of the earth's chief food growing zones.

　　  In the past, concern about a man-made warming of the earth has concentrated on the Arctic because the Antarctic is much colder and has a much thicker ice sheet. But the weather experts are now paying more attention to West Antarctic, which may be affected by only a few degrees of warming, in other words, by a warming on the scale that will possibly take place in the next fifty years from the burning of fuels.

　　  Satellite pictures show that large areas of Antarctic ice are already disappearing. The evidence available suggests that a warming has taken place. This fits the theory that carbon dioxide warms the earth.

　　  However, most of the fuel is burnt in the northern hemisphere, where temperatures seem to be falling. Scientists conclude , therefore, that up to now natural influences on the weather have gone beyond those caused by man. The question is: Which natural cause has most effect on the weather?

　　  One possibility is the variable behavior of the sun. Astronomers at one research station have studied the hot spots and "cold" spots (that is, the relatively less hot spots) on the sun. As the sun rotates (使旋转), every 27. 5 days, it presents hotter or "colder" faces to the earth, and different aspects to different parts of the earth. This seems to have a considerable effect on the distribution of the earth's atmospheric pressure, and consequently on wind circulation. The sun is also changeable over a long term: its heat output goes up and down in cycles, the latest trend being downward.

　　  Scientists are now finding shared relations between models of solar weather interactions and the actual climate over many thousands of years, including the last Ice Age. The problem is that the models are predicting that the world should be entering a new Ice Age and it is not. One way of solving this theoretical difficulty is to assume a delay of thousands of years while the solar effects overcome the inertia (惯性) of the earth's climate. If this is right, the warming effect of carbon dioxide might thus be serving as a useful opposed balance to the sun's fading heat .

It can be concluded that a concentration of carbon dioxide in the atmosphere would_________.

   A. mean a warming-up in the Antarctic

   B. raise the temperature of the earth' s surface

C. prevent the sun's rays from reaching the earth's surface

D. explain the cause of  great changes in the climate in the northern hemisphere

The article was written to explain ___________.

A. the greenhouse effect

B. the solar effects on the earth

C. the causes affecting weather

D. the models of solar-weather interactions

Although the fuel consumption is greater in the northern hemisphere, temperatures there　seem to be falling. This is__________.

A. mainly because the levels of carbon dioxide are rising

 B. partly due to changes in the output of solar energy

C. possibly because the ice caps in the poles are melting

D. only due to the effect of the inertia of the earth' s climate

On the basis of their models, scientists believe the opinion that__________.

A. the climate of the world should be becoming cooler

B. the new Ice Age will be delayed by the greenhouse effect

C. the man-made warming effect helps to increase the solar effects

D. it will take thousands of years for the inertia of the earth's climate to take effect

If the assumption about the delay of a new Ice age is correct, ____________.

A. ice would soon cover the northern hemisphere

B. the greenhouse effect could work in favor of the earth

C. the best way to overcome the cooling effect would be to burn more fuels

D. the increased levels of carbon dioxide in the atmosphere could warm up the earth even more quickly

D
　　In the atmosphere,carbon dioxide actd rather like a one-way mirror or the glass in the roof of a greenhouse which allows the sun's rays to enter but prevents the heat from excaping.
　　According to a weather expert's prediction,the atmosphere will be 3 warmer in the year 2050 than it is today, if man continues to burn luels at the present rate. If this warming up took place,the ice caps in the poles would begin to melt,thus raising sea level several meters and severely flooding coastal cities.Also，the increase in atmospheric temperature would lead to great changes in the climate of the northern hemisphere(半球),psooicbly resulting in an alteration of earth's chief food growing zones.
　　In the past,concern about a man - made warming of the earth has concentrated on the Arctic because the Antarctic is much colder and has a much thicker ice sheet.But the weather experts are now paying more attention to West Antarctic,which may be affected by a warming on the scale that will possibly take place in the next fifty years from on burning of fuels.
　　Satellite pictures showthat large areas of Antarctic ice are already disappearing.The evidence available suggests that a warming has taken place.This fits the theory that carbon dioxide warms the earth.
　　However,most of the fuel is burnt in the northern hemisphere,where temperatures seem to be falling.Scientists conclude,therefore,that up to now natural influences on the weather have exceeded those caused by man.The question is:Which natural cause has most effect on the weather?
　　One possibility is the variable behavior of the sun.Astronomers at one research station have studied the hot spots and cold spots(that is,the relatively less hot spots) on the sun. As the sun rotates(旋转),every 27.5 days,it presents hotter or colder faces to the earth,and different aspects to different parts of the earth.This seems to have a considerable effect on the distribution of the earth's atmospheric pressure,and consequently on wind circulation.The sun is also variable over a long term:its heat output goes up and down in cycles,the latest trend being downward.
　　Scientists are now finding mutual relations between models of solar weather interactions and the actual climate over many thousands of years ,including the last Ice Age.The problem is that the models are predicting that the world should be entering a new Ice Age and it is not.
　　One way of solving this theoretical difficulty is to assume a delay of thousands of years while the solar effects overcome the inertia(不活动，惰性) of the earth's climate.If this is right,the warming effect of carbon dioxide might thus be serving as a useful counter balance to the sun's diminishing heat.
　　68.It can be concluded that a concentration of carbon dioxide in the atmosphere would ___.
　　　A.mean a warming - up im the Arctic
　　　B.raise the temperature of the earth's surface
　　　C.prevent the sun's rays from reaching the earth's surface
　　　D.account for great changes in the climate in the northern hemiphere
　　69.Although the fuel consumption is greater in the northern hemisphere,temperatures there seem to be falling.This is _______.
　　　A.mainly because the levels of carbon dioxide are rising
　　　B.partly due to variations in the output of solar energy
　　　C.possibly because the ice caps in the poles are melting
　　　D.exclusively due to the effect of the inertia of the earth's climate
　　70.On the basis of their models,scientists are of the opinion that ________.
　　　A.the climate of the world should be becoming cooler
　　　B.the new Ice Age will be delayed by the greenhouse effect
　　　C.the man - made warming effect helps to increase the solar effects
　　　D.it will take thousands of years for the inertia of the earth's climate to take effect