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 _小题1:___ into sand.

B: And why?

A: Because people have __小题2:___ down a lot of trees.

B: That may be the root(根源). We should __小题3:__ people from cutting down trees. Although we have built “ the Great Green Wall”, we still need to work hard to __小题4:___ the environment.

A: I agree _小题5:__ you. Let’s go to the hill and plant trees on Sunday.

B:Good idea.

_______ makes the school famous is_______more than 90% of the students have been admitted to universities.

A．What;because

B．That;because

C．That;what

D．What;that