Question

He failed in the exams and only then _____ how much time he had wasted.

1. A.
   he realized
2. B.
   did he realize
3. C.
   he had realized
4. D.
   had he realized

Answer 1

B
试题分析：考查ｏｎｌｙ的倒装句，ｏｎｌｙ接状语的时候，谓语动词用部分倒装，ｔｈｅｎ这里是时间状语，句意：当他考试失败了，只有那时他才意识到浪费了多少时间。时态应该是一般过去时，选Ｂ。
考点：考查倒装句的用法
点评; only的倒装句要注意一定是only后面接状语才能倒装，如果接主语或宾语就不是倒装句了。