19. No sooner had we reached the top of the hill ____ we all sat down to rest.

　 A. when　　 　　　　　　 B. then　　 　　　　　 C. than　 　　　　　　　　　　 D. until

18. I felt somewhat disappointed and was about to leave ____ something occurred which attracted my attention.

　 A. unless　 　　　　　　 B. until　 　　　　　　 C. when　 　　　　　　　　　 D. while

17. I was just to go out ____ it began to rain.

　 A. as　　 　　　　　　　　 B. when　　 　　　　 C. after　　 　　　　　　　　 D. whole

16. Michael used to look hurt and surprised when ____ .

　 A. scolding　 　　　　　 B. to scold　 　　　　 C. having scolded　 　　 D. scolded

15. ____ the calculation is right, scientists can never be sure that they have included all variables and modeled them accurately.

　 A. Even if　　 　　　　　 B. As far as　 　　　 C. If only　 　　　　　　　　 D. So long as

14. Excuse me. If your call’s not too urgent, do you mind ____ mine first.

　 A. I make　　 　　　　　 B. if I make　　 　　 C. me to make　　 　　　　　　　 D. that I make

13. Although he knew little about the large amount of work done in the field, he succeeded ____

other more well-informed experimenters failed.

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

12. ____ that he is only a beginner, it is understandable for him to make such mistakes.

　 A. Considering　 　　 B. Considered　 　 C. Consider　 　　　　　　　 D. To consider

11. These two areas are similar ____ they both have a high rainfall during this season.

A. to that　　 　　　　　 B. besides that 　　　 C. in that　　 　　　　　　　 D. except that

10.The protection device can help to eliminate the possible faults ______they cause more

damage.

　 A. unless　　　　 　 B. although　　 　 C. until　　　　　 　　　 D. before