题目

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 much rain．But they still don’t become deserts．This is because some green plants are growing there．Smal 已知幂函数y＝f(x)的图象过点，则log2f(2)＝_________．