Scientists say it may be five or six years _______ it is possible to test this m
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Scientists say it may be five or six years _______ it is possible to test this medicine on human patients.A.since | B.after | C.before | D.when |
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答案
C |
解析
此题考查几个时间连词在状语从句中的区别。five or six years 是时间段,就应该找能表示点与点之间关系的连词。since+过去时间点,主句常用现在完成时;after无法确定时间段;when只表点,不表段;所以用before表从现在到测试那一天。 |
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