20. -You should have thanked her before you left.

-I meant _______ , but when I was leaving I couldn’t find her anywhere.

A. to do B. to C. doing D. doing so

19. -You seem to show interest in cooking.

-What? _______ , I’m getting tired of it.

A. On the contrary B. To the contrary　C. On the other hand D. To the other hand

18. While building a tunnel through the mountain, _______ .

A. an underground lake was discovered　B. there was an underground lake discovered

C. a lake was discovered underground　D. the workers discovered an underground lake　

17. These houses are sold at such a low price _______ people expected.

A. like B. as C. that D. which　

16. Every possible means _______ to prevent the air pollution, but the sky is still not clear.

A. is used B. are used　C. has been used D. have been used　

15. I shall stay in the hotel all day _______ there is news of the missing child.

A. in case B. no matter　C. in any case D. ever since　

14. I should have been there, but I _______ not find the time.

A. would B. could C. might D. should　

13. There was no news;_______ , she did not give up hope.

A. moreover B. therefore　C. but D. nevertheless　

12. Will those _______ the children from abroad come to the headmaster’s office?

A. teaching B. teach　C. who teaches D. who teaching　

11. I told him what I was surprised _______ his attitude towards his study.

A. is B. was C. at is D. at was