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¡¡¡¡51.The U.S. achieved its predominance after World War¢òbecause .

¡¡¡¡[A]it had made painstaking efforts towards this goal

¡¡¡¡[B]its domestic market was eight times larger than before

¡¡¡¡[C]the war had destroyed the economies of most potential competitors

¡¡¡¡[D]the unparalleled size of its workforce had given an impetus to its economy

¡¡¡¡52.The loss of U.S. predominance in the world economy in the 1980s is manifested in the fact that the American .

¡¡¡¡[A]TV industry had withdrawn to its domestic market

¡¡¡¡[B]semiconductor industry had been taken over by foreign enterprises

¡¡¡¡[C]machineª²tool industry had collapsed after suicidal actions

¡¡¡¡[D]auto industry had lost part of its domestic market

¡¡¡¡53.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.

¡¡¡¡54.The author seems to believe the revival of the U.S. economy in the 1990s can be attributed to the .

¡¡¡¡[A]turning of the business cycle[B]restructuring of industry

¡¡¡¡[C]improved business management[D]success in education

¡¡¡¡Passage2

¡¡¡¡Being a man has always been dangerous. There are about 105 males born for every 100 females, but this ratio drops to near balance at the age of maturity, and among 70-year-olds there are twice as many women as men. But the great universal of male mortality is being changed. Now, boy babies survive almost as well as girls do. This means that, for the first time, there will be an excess of boys in those crucial years when they are searching for a mate. More important, another chance for natural selection has been removed. Fifty years ago, the chance of a baby £¨particularly a boy baby£© surviving depended on its weight. A kilogram too light or too heavy meant almost certain death. Today it makes almost no difference. Since much of the variation is due to genes, one more agent of evolution has gone.

¡¡¡¡There is another way to commit evolutionary suicide; stay alive, but have fewer children. Few people are as fertile as in the past. Except in some religious communities, very few women have 15 children. Nowadays the number of births, like the age of death, has become average. Most of us have roughly the same number of offspring. Again, differences between people and the opportunity for natural selection to take advantage of it have diminished. India shows what is happening. The country offers wealth for a few in the great cities and poverty for the remaining tribal peoples. The grand mediocrity of today¡ªeveryone being the same in survival and number of offspring¡ªmeans that natural selection has lost 80% of its power in upperª²middle class India compared to the tribes.