Scientists are trying to make the deserts(沙漠) into good land again. They want to bring water to the deserts，so people can live and grow food. They are learning a lot about the deserts. But more and more of the earth is becoming desert all the time. Scientists may not be able to change the deserts. People are doing bad things to the earth.
Some places on the earth don't get much rain. But they still don't become desert. This is because some green plants are growing there. Small green plants and grass are very helpful to dry places. Plants don't let the hot sun make the earth even drier. Plants don't let the wind blow the earth(泥土) away.When a little bit of rain falls，the plants hold the water.Without the plants，the land can become a desert much more easily.
Why can the land become a desert?

A．Some places don't get much rain.

B．Plants don't let the hot sun make the earth even drier.

C．People are doing bad things to the earth.

D．Scientists haven't learnt enough about the deserts.

Scientists ______to make the deserts into good land again.

A．carry water	B．grow food
C．do nothing	D．study a lot

Which is NOT true?

A．The land never stops becoming desert.

B．Scientists ask the people to live in the deserts and grow food there.

C．People do bad things to the earth.

D．Scientists may not be able to change the deserts.

Why are green plants and grass helpful?

A．They can hold the water.

B．They can stop the wind from blowing the earth away.

C．They can keep the earth wet.

D．All the above are right.

Which is the best title(题目) for the passage?

A．The Desert Problem.

B．People Make Deserts.

C．Green Plants and Grass.

D．The Desert，the Tree and theWater.