用括号中所给的动词的适当形式填空。

1. You must _____ (look) after your pet dog. Don't let it run here and there.

2. —What's behind the door?

    —There _____ (be) two balls.

3. —Why not _____ (sing) an English song together?

    — Good idea.

4. There _____ (be) some money in that purse.

5. We are planning _____ (go) for a picnic this Sunday.

6. It often _____ (rain) here in summer.

7. You must remember _____ (close) the window when school is over.

8. The students are busy _____ (do) their homework.

9. _____ (skate) is my favorite sport.

10. There _____ (be)a pen and some books on the desk.