He failed in his business a third time and only then the difficult situation he was in. A

问题补充：

He failed in his business a third time and only then the difficult situation he was in.

A. I realized

B. I had realized

C. had I realized

D. did I realize

答案：

A. I realized

B. I had realized

C. had I realized

(答案→)D. did I realize

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