Scientists say it may be five or six years______this medicine is tested on human

游客2024-01-20  19

问题 Scientists say it may be five or six years______this medicine is tested on human beings.

选项 A、since
B、before
C、after
D、when

答案 B

解析 考察时间状语的连接词,根据题意是说“科学家们说大概要等5到6年,这种药才会在人类身上试验。”before引导时间状语从句,表示“在…之前”。
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