阅读下面短文，按照句子结构的语法性和上下文连贯的要求，在空格处填入一个适当的词或使用括号中词语的正确形式填空，并将答案填写在答题卡的相应位置上。

If the population of the Earth keeps on increasing at its present rate there will eventually not be enough resources 1.________(leave) to support life on the planet. By the middle of the 21st century if present trends continue we2._________（use）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 the earth will make 3. ______ necessary for us to look for open space somewhere else. But4.______ of the other planets in our solar system are capable of supporting life at present. One possible solution5.______ the problem 6._________ has recently been suggested by an American scientist Professor Carl Sagan. Sagan believes 7._______ before the Earth’s resources are 8._______(complete) exhausted it will be possible to change the atmosphere of Venus and therefore create a

new world almost as large as the Earth9. .The difficulty is that Venus is much hotter than the Earth. 10.________ there is only a tiny amount of water there.