Scientists say it still needs five or six years _____ it is possible for human p

题型：北京市期末题难度：来源：

Scientists say it still needs five or six years _____ it is possible for human patients to take this medicine. [ ]
A. since
B. before
C. after
D. when

答案

举一反三

—It"s a long story, but there are not any new words in it.
—Good! _______ it will be hard for children. [ ]
A. So
B. Or
C. But
D. And

题型：北京市期末题难度：| 查看答案

I haven"t heard from Bill _____ he left here. [ ]
A. when
B. before
C. since
D. while

题型：江苏省期末题难度：| 查看答案

Mr Smith usually reads a newspaper _____ he"s waiting for the bus. [ ]
A. if
B. then
C. because
D. while

题型：江苏省期末题难度：| 查看答案

—Please wait here . I"ll come back soon.
—All right. We"ll stay at the library ______ you come back. [ ]
A. until
B. for
C. while
D. as

题型：天津市期末题难度：| 查看答案

Someone called me at midnight, but he hung up _____ I could answer it. [ ]
A. as
B. since
C. after
D. before

题型：天津模拟题难度：| 查看答案