( ) 21. Stop smoking, _______ you will get better soon.

　　A. and B. or C. that D. after

　　( ) 22. Gray didn’t recognize his old classmate ________ he was told her name.

　　A. when B. unless C. so D. until

　　( ) 23. I was about to leave the office _______ the telephone rang.

　　A. when B. after C. before D. while

　　( ) 24. A lot of new buildings have been put up in our university. It is no longer the same _______ it used to be.

　　A. like what B. that C. as D. what

　　( ) 25. He is a scientist, ________ a singer as well.

　　A. but B. nor C. or D. and

　　( ) 26. John fell asleep ________ he was listening to the music.

　　A. after B. before C. while D. as soon as

　　( ) 27. ________ our football team failed in the match, we did our best.

　　A. Though B. But C. Because D. As

　　( ) 28. We bought Mary a present, _______ she didn’t like it.

　　A. and B. but C. or D. so

　　( ) 29. It was very late, _______ the students still went on repairing their desks and chairs.

　　A. and B. or C. so D. but

　　( ) 30. _______ China isn’t rich now, _______ we’re working hard to make her richer and richer.

　　A. Though; but B. Though; / C. Both; and D. Because; so