Only when I left for America how much I missed my parents.A. I realizedB. did I realizeC.

问题补充：

Only when I left for America how much I missed my parents.

A. I realized

B. did I realize

C. I had realized

D. had I realized

答案：

A. I realized

(答案→)B. did I realize

C. I had realized

D. had I realized

解析：only+状语位于句首句子采用部分倒装，根据句子意思看描述过去的事情应用一般过去时态。句意：只有当我到了美国我才意识到我多么想念我的父母。