莫高窟被称为世界最大的艺术宝库之一，主要原因是（　　）

—Good idea.

读下图完成下列各题。

Martin: What do you want to be when you grow up, Jiamin?

Jiamin: I want to be a fireman (消防员). I think the fireman is cool.

Martin: And you, Lily?

Lily: I like children. I want to be a teacher. What about you, Martin?

Martin: My father is a police officer. He can stop bad people. So I want to be a police officer.

Jiamin: Police officer can help people. Your father is great, Martin.

Martin: Thanks. Look, Miss Wang is hard-working. I think the teacher is great, too.