阅读理解。 Scientists are trying to make the deserts 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 desert in time. Why is more and more land becoming 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 (泥土) away. When a little bit of rain falls, the plants hold the water. Without plants, the land can become a desert much more easily. (from www.zkenglish.com ) 1. Desert is a large empty place, usually ______. [     ] A. almost nothing grows there B. there is very little rain C. people can live and grow food D. Both A and B 2. From the reading passage we know ______. [     ] A. land is becoming desert little by little B. the greatest desert in the world C. something about the hot desert wind D. nothing about the deserts 3. Scientists don't think that ______. [     ] A. we should bring water to the desert B. more and more of the earth is becoming desert C. people make the desert D. little rain makes good land become desert 4. Small green plants ______. [     ] A. need a lot of water B. are needed to dry places C. can hold much water than grass D. let the sun make the earth drier and drier 5. Which of these sentences is true? [     ] A. Plants let the wind blow the dirt away. B. All places without much rain will become deserts. C. Plants can stop dry land from becoming deserts. D. Land can't become desert faster than scientists can change it back into good land.