Scientists are trying to make the deserts ,which get very little rain, into good land agai

Scientists are trying to make the deserts ,which get very little rain, 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 being desert all the time. Scientists may not be able to change the desert in time．
Why is more and more land being desert？Scientists think that people make deserts．People are doing bad things to the earth against the scientists’ wish．
Some places on the earth don’t get much rain. But they still don’t bee 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 sun make the earth even drier． Plants do not let the wind blow the dirt away．When a bit of rain falls，the plants hold the water. Without plants, the land can bee desert more easily．
【小题1】Deserts      ． A．never have any plants or animals in themB．can all be turned into good land before longC．are being smaller and smallerD．get very little rain【小题2】More and more land is being desert  because    ． A．plants can’t grow thereB．there is not enough rainC．people haven’t done what scientists wish them to doD．scientists know little about the deserts【小题3】Small green plants are very important to dry places because     A．they don’t let the sun make the earth even drierB．they don’t let the wind blow the soil awayC．they hold waterD．All of the above．【小题4】After reading this passage, we learn that      ． A．plants can keep dry land from being desertB．it is good to get rid of the grass in the desertsC．all places without much rain will bee desertsD．it is better to grow crops on dry land than to cut themD