31. I think that something has to be done to stop our air from being polluted, _______?

A. doesn't it　　　　 B. hasn't it　　　 　　　 C. don't they　　 　 　　　 D. haven't they　　

30. ____ several times, but Mary still has no idea of how to do it properly.

A. Being shown　 B. Having shown 　　 C. Having been shown 　　 D. I’ve shown her

29. --- Has Sam finished his homework today?

--- I have no idea. He _____ it this morning.

A. was doing 　　　　　　　 B. has done　　　　 C. did　　　　　　 　　 D. had done 嘉定

28. After looking through the art books here, I found Andrew’s paintings to be the closest to _____ I thought good paintings should look.

A.　　　 how　　　　　　　　　　　 B. what　　　　　　　　 C. that　　　　　　　　 D. why

27.　 --- They believed that their conclusion was right, ____? --- I suppose so.

　　　 A. was it　　　　　　　 B. did they　　　　　　　　　 C.　　 didn’t they　　　　　 D. wasn’t it　 HP　

26. My little daughter has walked eight miles today. We never guessed that she could walk ______ far.

A. that　 　　 　　　　　 B. such　　　　　　　　 C. /　　　　　　　　　　　　　　 D. as

25. The efforts made by the researchers ____ possible the appearance of a new life- saving medicine.

A. were made　　　　　　　　　　 B. made 　　　　　　 C. made it　　　　　 D. were made it　 虹口

24. ________a large group, your tone should be clear and loud.

A. When addressed　 　　　　　　　　　　　　　　 B. While addressing　

C. When you address　 　　　　　　　　　　　　　 D. On addressing

23. Educators claim that children _______to English-speaking environment will learn the language more quickly.

　 A. being exposed　 B. to be exposed　　 C. having exposed　 D. exposed 奉贤

22. _____ on the floor of small ponds is a new farming industry.

　　　 A. Raising crabs 　　　 B. Crabs are raised　　 C. Crabs raised　　 D. Raised crabs