课时跟踪练(一) Welcome to the unit & Reading--Pre-reading

　　Ⅰ.阅读理解

　　A

　　If the earth's population is in growth at this rate, there will not be enough resources. By the middle of the 21st 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 the 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 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 the earth itself. The difficulty is that Venus is much hotter than the earth and there is only a tiny amount of water there.

　　Sagan proposes that algae organisms (海藻有机体) that can live in extremely hot or cold atmospheres and at the same time produce oxygen, should be bred in condition similar to those on Venus. As soon as this has been done, the algae will be placed in small rockets. Spaceship 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 work, 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 man to land on but the rain will eventually fall and in a few years something like the earth will be reproduced on Venus.

　　语篇解读：本文是一篇说明文。地球上的资源越来越少，人类的生存即将面临挑战。如何拯救地球上的人类？一些科学家提出了移民金星的建议，同时建议在地球资源耗尽之前在金星上培植一种海藻有机体，让金星产生与地球一样的生存环境。

　　1．In the long run, the most difficult problem caused by population growth on the earth will probably be the lack of________.

　　A．oil　　　　　　　　　　　 B．food

　　C．resources D．space

解析：选D　细节理解题。根据第一段第三句"Even if scientists develop new ways of feeding the human race ...look for open space somewhere else."可知，即使科学家开发出了供