Only when I left home to go to college how much my mother had done for me.A. did I realiz

问题补充：

Only when I left home to go to college how much my mother had done for me.

A. did I realize

B. I realized

C. had I realized

D. I had realized

答案：

(答案→)A. did I realize

B. I realized

C. had I realized

D. I had realized

解析：句意：只有当我离开家去上大学，我才意识到妈妈为我做了多少事情。这句话用only+时间状语从句，放在句首，后面的主句用部分倒装，助动词提前，因为realize这个动作，就是发生在when I left home to go to college，所以用一般过去时，所以选A。