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

问题补充：

I failed again in the examination and only then how 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：考查倒装句型。Only放句首时要求主句要使用部分倒装的句式。该句与前一句是并列关系，故事态一致/