Scientists are trying to make the deserts into good land again. They want to bring water t

o 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 desert. Scientists think that people make deserts. People are doing bad things to the earth.

Some places on the earth don't get very much rain. But they still don't become deserts. This is because some green plants are growing there. Small green plants and grass are very important to dry places. Plants don't let the hot sun make the earth even drier. Plants don't let the wind blow the dirt(土)away. When a little bit of rain falls, the plants hold the water. Without plants, the land can become a desert much more easily.

Deserts ______.

A．get very little rain

B．never have any plants or animals in them

C．can all be turned into good land before long

D．both A and C