题目内容：

补全对话。（每空一词，共5分）

A: What bad weather! Another sandstorm begins.

B: So it is. But why are there so many sandstorms recently?

A: Because there is so much sand around us.

B: Why is there so much sand?

A: Because a lot of land has been _1.___ into sand.

B: And why?

A: Because people have __2.___ down a lot of trees.

B: That may be the root(根源). We should __3.__ people from cutting down trees. Although we have built “ the Great Green Wall”, we still need to work hard to __4.___ the environment.

A: I agree _5.__ you. Let’s go to the hill and plant trees on Sunday.

B:Good idea.