【答案】　C

　　4．By writing the passage, the author tries to show .

　　A．we can do nothing without money

　　B．fathers are strict while mothers are kind

　　C．it's hard for parents to bring up their children

　　D．we should try to rely on ourselves for everything

　　【解析】　主旨大意题。作者开篇用一句歌词引出了主题：只要努力就能得到自己所需要的。中间用自己的一次经历进行了论证，最后一段在回扣"...trying my best to be a successful person.I believe that you can't always get what you want but if you try sometimes, you get what you need."，也就是"we should try to rely on ourselves for everything."

　　【答案】　D

　　B

　　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.