Question

By the time she left school ,she ___ that course for ten years.

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

Answer 1

选c
by the time 用完成时，是用将来完成时还是过去完成时要看语境，或者简单的就看从句的时态。
此题从句用过去时，所以主句一般也用过去时。
选D的话应该是would.

Answer 2

选C。
过去的过去，用过去完成时。
这句话的意思是“她离开学校的时候，已经教这门课教了10年了。”

Answer 3

可能是C吧。过去的过去。