I failed again in the examination and only thenhow much time I had wasted.A. I realizedB.

问题补充：

I failed again in the examination and only thenhow much time I had wasted.

A. I realized

B. I had realized

C. did I realize

D. had I realized

答案：

A. I realized

B. I had realized

(答案→)C. did I realize

D. had I realized

解析：考查倒装。only+状语放在句首时，句子要部分倒装。