阅读理解,Scientists are trying to make the deserts(沙漠) into good

阅读理解,
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 deserts all the time.Scientists may not be able to change the deserts .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 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 away.When a little bit of rain falls ,the plants hold the water.Without plants,the land can become a desert much more easily.
1 Why is more and more land becoming desert
2 What are scientists doing to the deserts
3 What can plants keep on the earth
4 Will all places without much water become deserts Why