While studying a map of China, have you ever noticed the Mu Us Desert(毛乌素沙漠)with a total area of about 42,200 square kilometers in the northwest? If you haven’t, then you probably never will. That’s because the desert is disappearing. You might want to know: Why is this happening? Who is the “killer”? Well, this is not a sad story. It is, instead, the result of years of afforestation(植树造林)efforts. The Mu Us used to be one of the largest deserts in China. Sandstorms were common in northern Shaanxi. Lots of people had to leave their homes.

The fight against desertification(沙漠化)began in the 1970s. The work was more than tiring. He Li’e led an afforestation team in Bulanghe, a town in Yulin, Shaanxi. They once spent a whole afternoon planting trees under the burning sun. That night, however, a strong wind blew away all the young trees. Crying was useless. The next day, the team planted all the trees again.

In Yulin, there are many other sandstorm fighters. One of them is Guo Chengwang. With encouragement from the government, in 1985, he started to plant trees in his village. Guo is now in his nineties. His children, grandchildren and great - grandchildren have continued the job. The family has turned 30 km of desert into woods. These trees have made a big difference. In Yulin, the number of sandy days has dropped from 100 in 2000 to 10 now.

With continuing efforts, the Mu Us Desert will be gone. It has changed from “looking for green in the sand” in the past to “looking for sand in the green.” Our motherland is becoming greener and lovelier.

A．

B．

C．

D．

The world is not hungry, but it is thirsty. It seems strange that nearly 3/4 of the Earth is covered with water while we say we are short of water. Why? Because about 97% of the water on the Earth is sea water which we can’t drink or use for watering plants directly. Man can only drink and use 3% of the water that comes from rivers and lakes. And we can’t even use all of that because some of it has been polluted.

Now more water is needed. The problem is: Can we avoid a serious water shortage later on? First, we should all learn how to save water. Second, we should find out the ways to reuse it. Scientists have always been making a study in this field. Today, in most large cities, water is used only once and then runs to the seas or rivers. However, it can be used again. Even if every large city reused its water, there still would not be enough water. What could people turn to next?

The sea seems to have the best answer. There is a lot of water in the sea. All that needs to be done is to get the salt out of the sea water. This is expensive, but it’s already in use in many parts of the world. Scientists are trying to find a cheaper way to do it. So you see, if we can find a way out, we’ll be in no danger of drying up.