Napoga is a 12-year-old girl in Ghana(加纳)，Africa. It is hard for her family to get clean water. Every morning，she leaves home at half past five to get clean water for her family in a village far away. It takes her six hours to get enough clean water for daily cooking and drinking. She has no time to go to school or to play with her friends. Millions of people in the world are like Napoga. They can't get enough clean water to keep healthy.
Earth Day is April 22. But on all other days，we must also remember it. The water we use is the most important natural resource(自然资源) on the earth.
Water covers 70% of the earth's surface. But most of that is sea water. We can't use it for very many things. Fresh water covers only 1% of the earth's surface.
You probably feel lucky that your life isn't as hard as Napoga's. But that doesn't mean you don't have to worry about water. We all face serious water problems. One of them is water pollution. All kinds of things from cars，factories，farms and homes make our rivers，lakes，and oceans dirty. Polluted water is very bad for people to drink. And dirty water is bad for fish，too. Now, 34% of all kinds of fish are dying out.
How do cars and factories make our water dirty？First，they pollute the air. Then，when it rains，the rain water comes down and makes our drinking water dirty. Dirty rain，called acid rain(酸雨)，is also bad for plants，animals and buildings.
Scientists say that in 30 years，more than half of the people in the world won't have enough clean water. We have to learn how to save more water for ourselves and our children. Here is some advice for saving water：
●Turn off the water while you brush your teeth. You can save as much as 450 liters(升) each month.
●Leaky taps(漏水的龙头) waste a lot of water. Fix them right away！
●You can easily cut your 10-minute showers in half----and you'll be just as clean.
●When you wash dishes，don't let the water run.
●Only wash clothes when you have a lot to wash. If your washing machine isn't full，you're  wasting water！
On the earth，_______.

A．sea water is more widely(广泛地) used than fresh water

B．there is very little water for our living

C．there is 71% of fresh water

D．we don't need to worry about water

Acid rain _______.

A．is only bad for living things

B．can be produced in factories

C．doesn't do harm(伤害) to people，but it's bad for plants，animals and buildings

D．doesn't just do harm to human beings but to animals，plants and buildings

Which of the following wastes water？

A．We need ten minutes if we want a clean shower.

B．We should put in enough clothes when we wash them in washing machines.

C．You can keep yourself clean by having a shower for five minutes.

D．Don't let the water run when we brush our teeth and wash dishes.

What's the main idea of the passage？

A．Something must be done to prevent water from being polluted.

B．Clean water means much to human beings and living things around us.

C．It's time to take care of the water we use.

D．Water is the most important natural resource on the earth.