Question

By the time she left school ,she ___ that course for ten years. A. taught B. has taught C. had tau

By the time she left school ,she ___ that course for ten years. A. taught B. has taught C. had taught D. will have taught 为什么不是用将来完成时？

Answer 1

正解是C 。
题目暗示点 是 By the time she left school
she left school 的动作发生在过去， by 在这里是 在某个时间以前。 在她离开学校以前， 那么teach 的动作发生在离开学校以前， 表示过去的过去， 用过去完成时had taught .

追问

如果把left改成leave 呢

追答

要是改为 leaves , 那就用将来完成时或现在完成时，取决于具体内容。

Answer 2

A？