用括号中的介词填空。

(on, like, after, at, in, of, under)

1. Is Li Lei ______ duty today?

2. My bike isn't ______ the tree. It's in the house.

3. What are these ______ English?

4. －Where is the broom?

    －I think it's ______ the floor.

5. －What's on the wall?

    －It's a map ______ China.