21. The picture _______ on the wall was painted by my son.

　 A.having hung　　 B. hanging　　 C.hangs　　 D. being hung

20. The flu is believed _______ by a certain kind of virus.

　 A.causing　　 B. being caused　　 C. to be caused　　　 D. to have caused

19. It is decided _________ the meeting has been put off till next Monday.

　 A. that　　 B. which　　　 C. what　　　　 D. when

18. It is pretty well understood _________ controls the flow of water.

17. The thief was reported _______ in London.

　 A.to be seen　 　 B.to have been seen　　　　　　 C.seeing 　　　　　　　　　　 D.having seen

16.-The college entrance exam is drawing near.

　 - So it is high time we _________ our lessons.

　A. get down to go over　　　　　　　　 B. got down to go over　　　　　　　

C. get down to going over　　　　　　 　　 D. got down to going over

15. You can write about ______ topic you prefer.

A.what　　　　　　　　 B.no matter what　　　　 C.whatever　　　　　　　　　 D.which

14. Actually, 　　　　　makes this shop different is that it offers more personal services.

13. It was in May ______ we heard the news ________ we won the game.

　A. when; where　　 B. that; that　　 C. when; that　　 D. that; where

12. It was after 20 years _______ he returned to the village _______ he had been brought up.