单项选择题

Questions 16 to 20 are hsed on the following passage. At the end of the possage, you will be given 15 seconds to answer the questions.
Now listen to the passage.

What do we learn from this passage

A.Man can change the balance of nature just as they please.
B.If the balance of nature is lost, it will be attained again.
C.Man must plant as many trees as possible.
D.Some desert areas are the nature’s punishment of the human beings for their ignoranc