17. Scientists say it may be five or six years _____ it is possible to test this medicine on human
patients.（2004-福建）
A. since B. after
C. before D. when
18. You should try to get a good night’s sleep much work you have to do.（2004-湖北）
A. however B. no matter
C. although D. whatever
19. We were told that we should follow the main road _____ we reached the central railway
station. （2004-辽宁）
A. whenever B. until
C. while D. wherever
20. ______ you call me to say you’re not coming, I'll see you at the theatre.（2004-全国II）
A. Though B. Whether
C. Until D. Unless
21. Several weeks had gone by _____ I realized the painting was missing.（2004-全国IV）
A. as B. before
C. since D. when
22. Jasmine was holidaying with her family in a wildlife park _____ she was bitten on the leg by
al lion.（2004-上海）
A. when B. while
C. since D. once
23. Parents should take seriously their children’s requests for sunglasses _____ eye protection is
necessary in sunny weather. （2004-上海）
A. because B. through
C. unless D. if
24. ______ , I have to put it away and focus my attention on study this week. (2004-上海春)
A. However the story is amusing B. No matter amusing the story is
C. However amusing the story is D. No matter how the story is amusing
25. It was evening ______ we reached the little town of Winchester. （2004-天津）
A. that B. until
C. since D. before
26. Don’t be afraid of asking for help _____ it is needed.（2003-全国）
A. unless B. since
C. although D. when
27. I would appreciate it _____ you call back this afternoon for the doctor’s appointment.（2003-
上海）
A. until B. if
C. when D. that
28. He was about to tell me the secret _____ someone patted him on the shoulder. (2002-上海)
A. as B. until
C. while D. when
29. The famous scientist grew up _____ he was born and in 1930 he came to Shanghai.（2002上
海春）
A. when B. whenever