Only when he told me what trouble he was in.A. did I realizeB. I realizedC. do I realizeD.

问题补充：

Only when he told me what trouble he was in.

A. did I realize

B. I realized

C. do I realize

D. I realize

答案：

(答案→)A. did I realize

B. I realized

C. do I realize

D. I realize

解析：考查倒装句。Only+when引导的状语从句提前主谓用部分倒装。又因为前后时态一致，故答案为A。