21.　You’d better come back earlier _______ it is getting colder.

A. as　　　 　　　　　B. and　　　　　　　 C. but　　　　　 　　D. or

20.　He always talks _______ he had been to outer space.

A. like　　 　　　　　B. as if /though　　 　　C. because of　 　　　D. as

19.　Persist to the end , _______ you are the only one left.

A. even if /though　 　B. but　　　　　　　　 C. however　　　　 　D. in spite of

18.　We’ll carry the work through , cost _______ it may .

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

17.　_______ you have got used to it , you’ll like it .

A. While　　　　　　 B. On the condition　 　C. Once　　　　　 　　D. Unless

16. I paid only 5 pounds for the book , _______I expected it would cost.

A. not as many as　　　　　　　　　　　　　 B. not so much as　　

C. cheaper than　　　　　　　　　　　　　　 D. not so expensive

15. _______I know , the computer can never take the place of the human brain.

A. As for　　　　　　 B. As long as　　　　 　C. So far for　　 　　　D. So /As far as

14. ______ did it , I didn’t.

A. Who　　　　　　　 B. Whoever　　　　　 C. No matter whom　　 D. No matter when　

13.I sent the letter early that morning _______ she got it that afternoon.

　A. in order that　　 　B. so that　　　　　 　C. for purpose that　　 　D. in order for

12.He wouldn’t give up smoking _______ his doctor told him it was a matter of life and death.

A. except　　　　　　 B. after　　　　　　 C. until　　　 　　　　D. in case