Scientists say it may be five years _____ it is possible to test this medicine o

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Scientists say it may be five years _____ it is possible to test this medicine on human patients.[ ]
A. since
B. until
C. before
D. when

答案

举一反三

The government has taken some measures to reconstruct the earthquake-hit areas, but it must be some time
____ everything returns to normal. [ ]
A. since
B. after
C. unless
D. before

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Try ____ she might, Sue couldn"t get the door open. [ ]
A. if
B. as
C. sine
D. when

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The fleet made several expeditions _____ the exploration was stopped. [ ]
A. when
B. before
C. while
D. since

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_____ children believe they can succeed, they will never become totally independent. [ ]
A. If
B. Though
C. Unless
D. When

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Tourism, _____ it brings in money to a country, can also result in damage to the World Heritage sites there. [ ]
A. because
B. as
C. while
D. since

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