20. ______ for years since I joined the army.

A. There was　　 B. There is　　 C. It is　　 D. It was

19. I took _______ for granted that he would believe in us.

A. that　　　 B. the thing　　 C. it　 　　　D. this

18. Tom’s mother kept telling him that he should work harder, but ______

　didn’t help.

A. he　　　 B. it　　　　 C. which　　　 D. she

17. Someone is ringing the doorbell. Go and see _________.

A. who is he　　 B. who it is　　 C. who is it　　　 D. who he is

从A、B、C、D四个选项中，选择可以填入空白处的最佳选项。

16. The boy became fatter and fatter each day and _______ made his parents sad.

A. which　　　 B. what　　　 C. he　　　 D. it