21. Open the door,__________?

20. He must　 have come here,___________?

19. He must　 have read the book,____________?

18. He must　 be at home ,___________?

17. We must study hard,_____________?

16. There will be a film tonight ,___________?

15. There is no air or water on the moon ,_____?

13. Those books aren't yours ,____________?

12. This dictionary is dear ,__________?

11. The Green's have been to the Great Wall ____?