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  3. If the population of the Earth goes on increasing at its present rate, there will eventually not be enough resources left to【B1】

If the population of the Earth goes on increasing at its present rate, there will eventually not be enough resources left to【B1】

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问题     If the population of the Earth goes on increasing at its present rate, there will eventually not be enough resources left to【B1】_____life on the planet. By the middle of the 21st century, if present trends continue, we will have【B2】_____all the oil that drives our cars, for example. Even if scientists develop new ways of 【B3】_____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【B4】_____ are capable of supporting life at present. One possible solution to the problem has recently been suggested by an American scientist, Prof. Carl Sagan.
    Prof. Sagan believes that before the earth’s resources are completely【B5】_____, it will be possible to change the atmosphere of Venus and so create a new world almost as large as Earth itself.
    Sagan proposes that algae(藻类), an【B6】_____that can live in extremely hot or cold atmospheres and at the same time produce oxygen, should be【B7】_____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【B8】_____short time, the algae will【B9】_____the carbon dioxide into oxygen and carbon.
    When the algae have done their work, the atmosphere will become cooler. The oxygen will produce rain and in a few years something like Earth will be【B10】_____on Venus.
【B1】
选项
答案sustain
解析 根据空格前的to可知，空格处应填入动词(词组)。结合录音可填入sustain，意为“维持”。
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