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If the population of the Earth goes on increasing at its present rate, there will eventually not be enough resources left to sus

admin2012-02-27  42
问题     If the population of the Earth goes on increasing at its present rate, there will eventually not be enough resources left to sustain life on the planet. By the middle of the 21 century, if present trends continue, we will have used up all the oil that drives our cars, for example. Even if scientists develop new ways of feeding the human race, the crowded conditions on Earth will make it necessary for us to look for open space somewhere else. But none of the other planets in our solar system are capable of supporting life at present. One possible solution to the problem, however, has recently been suggested by an American scientist, Professor Carl Sagan.
    Sagan believes that before the Earth’s resources are completely exhausted, it will be possible to change the atmosphere of Venus and so create a new world almost as large as Earth itself. The difficulty is that Venus is much hotter than the Earth and there is only a tiny amount of water there.
    Sagan proposed that algae, organisms that can live in extremely hot or cold atmospheres and at the same time produce oxygen, should be bred in conditions similar to those on Venus. As soon as this has been done, the algae will be placed in small rockets. Spaceships will then fly to Venus and fire the rockets into the atmosphere. In a fairly short time, the algae will break down the carbon dioxide into oxygen and carbon.
    When the algae have done their works, the atmosphere will become cooler but before man can set foot on Venus, it will be necessary for the oxygen to produce rain. The surface of the planet will still be too hot for men to land on it but the rain will eventually fall and in a few years something like Earth will be reproduced on Venus.
    If the experiments are successful, life will become possible there, but it will not be pleasant at first. When they go to Venus, the first colonists will have to take plenty of water with them and get used to days and nights lasting 60 Earth-days. But there will also be some advantages. The colonists will live longer because their hearts will suffer less strain than on Earth. Apart from that, they will be exploiting a new world while those still on Earth are living in closed, uncomfortable conditions. Perhaps it will be the only way to ensure the survival of the human race.
It will eventually become necessary for us to try to colonize another planet because ______.
选项 A、the Earth will have too many people on it
B、we’ll have used all the oil that drives our cars
C、there are not enough resources to sustain life on Earth
D、other planets in solar system can support life now
答案C
解析 本题是细节题。文中第一段说得很清楚If the population of the Earth goes on increasing at its present rate…we will have used up all the oil that drives our cars，for example．之所以需要开发另一行星，其根本原因是地球上没有足够的资源来维持人们的生存。故A、B、D均非根本原因，不符合题意。所以C选项是正确答案。
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