Look at the Earth from.space.Why does our planet look so blue？Its blue because water covers almost three quarters of the Earth's surface.Water is not just an important part of our planet.It is an important part of our body，too.More than half of our total body weight is water.

    Our body loses water whenever we exercise or.go to the toilet.That's why we need to drink plenty of water every day.We drink water.We use it to cook，clean，and carry waste out of our homes.Farmers use it to grow vegetables and crops like rice and corn；factories use it to make products.

    Since the 1950s，the amount（数量）of water people use has increased by three times.But the water supply（供应）hasn't.Scientists worry that soon there won't be enough water for us，as well as for the animals and plants that share our world.What can we do to help？Use water wisely.

    Having enough water isn't our only problem. We also need it clean.

    Right now，ships and factories are putting wastes into seas，rivers and so on.Even chemicals that farmers use are running into rivers and lakes.All this pollution can make the water dangerous to drink.It can also harm fish and other water﹣living lives.

    We must do something to stop pollution.It's the best way to protect our world's most valuable natural resource（资源）.

（1）How many important areas of water are mentioned in Paragraph 1？ 　 　

A.One.

B.Two.

C.Three.

D.Four.

（2）The underlined sentence "We also need it clean" in Paragraph 4 means"     　."

A.We also need water to wash things

B.We also need water that looks clean

C.We also need to keep water clean

D.We also need to discover clean water

（3）This passage was written to 　 　.

A.ask people to value water

B.advise people to drink more water

C.introduce the uses of water

D.describe the situation of water supply