题目内容
【题目】By the time Einstein was 14 years old, he himself advanced mathematics.
A. has taught
B. taught
C. had taught
D. was teaching
【答案】C
【解析】 by the time引导时间状语从句;主句动作发生在从句动作之前,故用过去完成时。
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题目内容
【题目】By the time Einstein was 14 years old, he himself advanced mathematics.
A. has taught
B. taught
C. had taught
D. was teaching
【答案】C
【解析】 by the time引导时间状语从句;主句动作发生在从句动作之前,故用过去完成时。