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选修7 Unit 5 Travelling abroad 能力演练 一、语法填空 If the population of the Earth keeps on 1 (increase)at its present rate,there will 2 (event)not be enough resources left to support life on the planet.By the middle of the 21st century,if present trends continue,we 3 (use)up all the oil that drive our cars,for example.Even if scientists develop new ways of feeding the human race,the crowded conditions on Earth will make it 4 (necessity)for us to look for somewhere else.But 5 of the other planets in our solar system are capable of supporting life at present.One possible solution to the problem, 6 ,hasrecentlybeen suggested by an American scientist,Professor Carl Sagan.Sagan believes that 7 the Earth,s resources are completely 8 (exhaust),it will be possible to change the atmosphere of Venus and 9 create a new world almost as large as Earth itself.Something is difficult.Venus is much hotter than the Earth. 10 ,there is only a tinyamountof water there. | 
