阅读理解。

   The world is not only hungry, but it is also thirsty for water. This may seem strange to you, since nearly

70% of the earth's surface (表面) is covered with water. But about 97% of that is sea water, or salt water.

Man can only use the other 3% the fresh water from rivers, lakes, underground, and other sources (源泉).

And we can not even use all of that. Even worse, some of it has been made dirty.

    However, as things stand today, this fresh water is still enough for us. But our need for water is becoming

larger and larger quickly-almost day by day. We should take steps to do with this problem now and in this

way we can get away from a serious world-wide water shortage (缺乏) later on.

    We all have to learn how to stop wasting (浪费) our valuable water. One of the first steps is to develop

(开发) ways of reusing it. Today in most large cities, water is used only once and then sent out into a sewer

system(下水道). From there it returns to sea or runs into underground places. But even if every large city

reused its water, we still would not have enough. All we'd have to do to make use of sea water in the world

is to remove the salt. If we take these we will be in no danger of drying up.

1. The world is thirsty for water because ___. [ ]

A. man has not got enough food to eat

B. we haven't got enough fresh water

C. only 70% of the earth's surface is water

D. more water is sent into sewer system

2. The underlined word "valuable" means ___ and ___. [ ]

A. much, salty

B. fresh, enough

C. dear, useful

D. clean, helpful

3. What should we do if we want to have enough fresh water? ___. [ ]

A. Make full use of the sea water

B. Carry salt water into lakes or rivers

C. Try to save the fresh water as much as possible

D. Do our best to use the water again

4. The best but the most difficult way to solve (解决) the water problem of the world is to ___. [ ]

A. remove the salt from sea water

B. make the water in cities clean

C. take the water from underground

D. make the need for water smaller

5. What is the best title for this passage? ___. [ ]

A. The Importance of the Water

B. The World's Water Problem

C. The Thirsty World

D. Fresh Water and Sea Water