Question

I failed in the final examination last term and only then __ the importance of studies.

A. I realized B. I had realized C. had I realized D. did I realize
答案选D 为什么不能选A呢？

Answer 1

I failed in the final examination last term and only then __ the importance of studies.
A. I realized B. I had realized C. had I realized D. did I realize
选D
这是一句only引导的状语从句放句首引起的部分倒装
结构是
only+状语从句+助动词+主语+谓语（动词）+宾语
所以选D
有不会的可以再问我

Answer 2

因为强调 only then， 所以后面的句子里的 主语 I 和 谓语 realized 要倒置，就成了 did I realize

Answer 3

要到装的 only then

Answer 4

D
倒装

Answer 5

only then 出现要用倒装