35. _________such heavy pollution already, it may now be too late to clean up the river.

　 A. Having suffered　 B. Suffering　　 C. To suffer　　 D. Suffered

34. _________is known to everybody, the moon travels round the earth once every month.

　 A. it　 B. As　　 C. That　　 D. What

33. I was really anxious about you. You_________home without a word.

　 A. mustn’t leave　　 B. shouldn’t have left　 C. couldn’t have left　 D. needn’t leave

32. Visitors_________not to touch the exhibits.

　 A. will request　　 B. request　　 .C. are requestiong　　 D. are requested

31. A computer can only do_________you have instructed it to do.

　 A. how　　 B. after　　 C. what　　 D. when

30. I _________ping-pong quite well, but I haven’t had time to play since th enew year.

　 A. will play　 B. have played　 C. played　 D. play

29. The warmth of_________sweater will of course be determined by the sort of_________wool used.

　　 A. the; the　　 B. the;/　　 C. /; the　　 D. /; /