问题
选择题
He failed the midterm examination and only then ________how much time he had wasted.
A．he realized
B．did he realize
C．he had realized
D．had he realized
答案
答案：B
本题考查动词的时态和倒装句的用法。根据语法要求only引导状语位于句首时，需要使用倒装句结构。而该状语only then表明了动作发生在过去。
