How will our continuously growing population affect our way of life, our environment, even our planet? No matter how you look at it, we will face     1     extremely serious problem. By the middle of the 21st century, we will have used up all the oil that     2     (drive)our cars if at the rate we’re going. Even if scientists develop some new     3     (way)of feeding the human race, the crowded conditions on the earth will make     4     necessary for us to look for open space somewhere else. But none of the planets in our solar system are able     5     (support)life at present. One possible solution     6     the problem, however, has recently been raised by an American scientist, Professor Carl Sagan. His idea is     7     before the earth’s resource are almost exhausted, it will be     8     (total)possible to change the atmosphere of Venus(金星) and so create a new world almost as large as earth itself.

However,     9     his idea is turned into reality, humans have a long way to go. On the one hand, Venus is much     10     (hot)than the earth; on the other hand, there is only a tiny amount of water there.