Forests have always been useful and important to man who make use of them in many ways. Ev
If there were no trees, heavy rains would wash away the rich top soil that is so important to plants. The result is that the land will become a desert. There are plenty of desert areas in the world. A long time ago these desert areas used to be very rich areas, but man in the past had not enough knowledge about science of nature, they cut down too many trees in the area where they lived and never planted new ones. By and by the rich top soil was blown and washed away by strong winds and heavy rains. In the end the rich land changed into useless deserts where nothing could grow.
According to the passage, ______.
A.a long time ago, man did not know how to make use of wood
B.trees are not as useful as they were in the past
C.trees were more found in the past than they are today
D.people have 'always found trees useful