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

　　What comes into your mind when you think about robots? Do you imagine armies of evil metal monsters planning to take over the world? Or, perhaps of mechanical men who have been created as guards or soldiers by a mad genius? Or maybe you think of man- like robots who act, think, and look like human beings. In fact robots like these have more to do with science fiction films than with real life. In the real world robots are machines that do jobs which otherwise have to be done by people. Robots either operate by themselves or under the control of a person.
　　In a car factory, for example, robot machinery can put together and paint car bodies. On the sea bed remotecontrolled（遥控）underwater machines with mechanical arms can perform tasks too difficult for divers. Robot spacecraft can explore the solar system and send back information about planets and stars.
　　Many robots have computer brains. Some robots are fitted with cameras , sensors, and microphones which enable them to see, to feel, and to hear. And some robots can even produce electronic speech.
　　All this does not mean that a robot can think and behave like a human being. Present day robots have to be programmed with a good deal of information before they can carry out even simple tasks.
　44．Robots in real life________.
　　A. can behave like human beings   B. have the ability to control the world
　　C. can think by themselves        D. can help us with a lot of work
　45．According to this article, which of the following is not true about robots in the real world?
　　A. Some robots are as creative as artists.     B. Some robots can help manufacture cars.
　　C. Some robots can see and hear.       D. Some robots can explore outer space.
　46．Robots can perform many tasks for man because________.
　　A. they have intelligence    B. they are supplied with computer programs
　　C. they can imitate human beings    D. they have the ability to learn new things
　47．The robots in science fiction films and those in real life differ mainly in________.
　　A. mentality　　 B. appearance　　 C. material　　　 D. size

　　What comes into your mind when you think about robots? Do you imagine armies of evil metal monsters planning to take over the world? Or, perhaps of mechanical men who have been created as guards or soldiers by a mad genius? Or maybe you think of man- like robots who act, think, and look like human beings. In fact robots like these have more to do with science fiction films than with real life. In the real world robots are machines that do jobs which otherwise have to be done by people. Robots either operate by themselves or under the control of a person.

　　In a car factory, for example, robot machinery can put together and paint car bodies. On the sea bed remotecontrolled（遥控）underwater machines with mechanical arms can perform tasks too difficult for divers. Robot spacecraft can explore the solar system and send back information about planets and stars.

　　Many robots have computer brains. Some robots are fitted with cameras , sensors, and microphones which enable them to see, to feel, and to hear. And some robots can even produce electronic speech.

　　All this does not mean that a robot can think and behave like a human being. Present day robots have to be programmed with a good deal of information before they can carry out even simple tasks.

　44．Robots in real life________.

　　A. can behave like human beings   B. have the ability to control the world

　　C. can think by themselves        D. can help us with a lot of work

　45．According to this article, which of the following is not true about robots in the real world?

　　A. Some robots are as creative as artists.     B. Some robots can help manufacture cars.

　　C. Some robots can see and hear.       D. Some robots can explore outer space.

　46．Robots can perform many tasks for man because________.

　　A. they have intelligence    B. they are supplied with computer programs

　　C. they can imitate human beings    D. they have the ability to learn new things

　47．The robots in science fiction films and those in real life differ mainly in________.

　　A. mentality　　 B. appearance　　 C. material　　　 D. size

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