He devoted his life to __________ the atomic theory.

　 A. study　　　　 B. be studied　　 C. studying　　　　 D. have studied

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

　　Decision-thinking is not unlike. It often matters not only what you think, but also what others think you think and what you think they think you think. The mental process（过程） is similar. Naturally, this card game has often been of considerable interest to people who are, by any standards, good thinkers.
　　The great mathematician John von Neumann was one of the founders of game theory. In particular, he showed that all games fall into two classes; there are what he called games of 'perfect information', games like chess where the players can't hide anything or play tricks; they don't win by chance, but by means of logic and skills. Then there are games of 'imperfect information', like poker, in which it is impossible to know in advance that one course of action is better than another.
　　One mistaken idea about business is that it can be treated as a game of perfect information. Quite the reverse, business and life itself are games which we must normally play with very imperfect information. Business decisions are often made with many unknown and unknowable factors（因素）, as best poker players. But few business people find it comfortable to admit that they are taking a chance, and many still prefer to believe that they are playing chess, not poker.
49．The subject discussed in this text is _________.
　　A．the process of reaching decisions
　　B．the difference between poker and chess.
　　C．the secret of making good business plans
　　D．the value of information in winning games
50．An important factor in a game of imperfect information is ___________.
　　A．rules               B．luck         C．time               D．ideas
51．Which of the following can be used in place of "Quite the reverse"?
　　A．Quite right.                   B．True enough.
　　C．Most unlikely.                      D．Just the opposite.
52．In the writer's opinion, when making business decisions one should ___________ .
　　A．put perfect information before imperfect information
　　B．accept the existence of unknown factors
　　C．regard business as a game of chess
　　D．mix known and unknown factors

A landing on Mars is within the _____ of current physical theory.

　　A. scheme    B. scope    C. scrap    D. scale

When I come across a good article in reading newspapers, I often want to cut and keep it. But just as I am about to do so, I find the article on the __1__ side is as much interesting. It may be a discussion of the way to __2__ in good health, or __3__ about how to behave and conduct oneself in society. If I cut the front article, the opposite one is likely to __4__ damage, leaving out half of it or keeping the text __5__ the title. Therefore, the scissors would __6__ before they start, __7__ halfway done when I find out the __8__ result.

Sometimes two things are to be done at the same time, both worth your __9__. You can only take up one of them, the other has to wait or be __10__ up.

But you know the future is unpredictable—the changed situation may not allow you to do what is left__11__. Thus you are __12__ in a difficult position and feel sad. How __13__ that nice chances and brilliant ideas should gather around all at once? It may happen that your life __14__ greatly on your preference of one choice to the other.

In fact that is what __15__ is like: we are often __16__ with the two opposite sides of a thing which are both desirable like a newspaper cutting. It often occurs that your attention is drawn to one thing only __17__ we get into another. The __18__ may be more important than the latter and give rise to divided mind. I __19__ remember a philosopher's remarks, “When one door shuts, another opens in life.” So a casual __20__ may not be a bad one.

1.A.front　　　　 B．same　　　　　　 C．either　　　　 D．opposite

2．A.get　　　　　 B．keep　　　　　　 C．lead　　　　　 D．bring

3．A.advice　　　 B．news　　　　　　 C．a theory　　　 D．a report

4．A.suffer　　　 B．reduce　　　　　 C．prevent　　　 D．cause

5．A.on　　　　　 B．for　　　　　　 C．without　　　 D．off

6．A.use　　　　　 B．handle　　　　　 C．prepare　　　 D．stay

7．A.or　　　　　 B．but　　　　　　 C．so　　　　　　 D．for

8．A.satisfying　 B．regretful　　　 C．surprising　　 D．impossible

9．A.courage　　　 B．strength　　　　 C．attention　　 D．patience

10．A.given　　　 B．held　　　　　　 C．made　　　　　 D．picked

11．A.near　　　　 B．alone　　　　　 C．about　　　　 D．behind

12．A.filled　　　 B．attracted　　　 C．caught　　　　 D．struck

13．A.dare　　　　 B．come　 　　　　 C．deal　　　　　 D．do

14．A.improves　　 B．changes　　　　 C．progresses　　 D．goes

15．A.study　　　 B．society　　　　 C．nature　　　　 D．life

16．A.faced　　　 B．supplied　　　　 C．connected　　 D．fixed

17．A.before　　　 B．after　　　　　 C．until　　　　 D．as

18．A.following　 B．next　　　　　　 C．above　　　　 D．former

19．A.still　　　　 B．also　　　　　　 C．once　　　　　 D．almost

20．A.treatment　　 B．action　　　　　 C．choice　　　　 D．remark