2. 外语
  3. Are we at the beginning of another Age of Exploration? Perhaps even more important, are we at the beginning of【C1】______Age of C

Are we at the beginning of another Age of Exploration? Perhaps even more important, are we at the beginning of【C1】______Age of C

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问题     Are we at the beginning of another Age of Exploration? Perhaps even more important, are we at the beginning of【C1】______Age of Colonization? As the population of the world increases towards the point【C2】______the earth can no longer support all the people【C3】______on it, the second question becomes urgent. Will we discover a new world, 【C4】______Columbus did, on which human life will be possible? At this point in the space age, no one can really answer these questions. We can say, 【C5】______that we will not see tomorrow the kind of space travel that【C6】______fiction and the movies have shown. It will be a long time before we have flight that run【C7】______to human colonies on the moon or on, one of the planets. We are not even going to be able to【C8】______immediate advantages of the minerals that we may find on the planets【C9】______our own solar system.
    Great problems must be solved【C10】______we could send colonists out into place. The distances that must be【C11】______and the length of time it takes to do that can hardly be【C12】______There are also dangers that we still do not realty understand, from radiation, for example, or from pieces of matter【C13】______in space, or from contamination forms of life that might【C14】______there. There is also need for humans to take their own environment into space【C15】______them. So far no "island" has been discovered in space on which people can exist without systems that【C16】______life, and these systems must accompany any future space【C17】______Finally, on the most practical【C18】______there has to be enormous expense【C19】______in space exploration. The U. S. and Russian governments have already spent billions of dollars for projects【C20】______which they can receive a return only in knowledge and not in money.
【C10】
选项 A、after
B、till
C、before
D、until
答案C
解析 上下文语义。根据句意为：Great problems当然应该在我们送colonists上太空以前解决，所以应选before。故答案为C。
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