问题
选择题
Only when I left my parents for America ____ how much I loved them.
A．I realized
B．I had realized
C．had I realized
D．did I realize
答案
答案：D
考查倒装。Only+ when引导的时间状语从句放在句首时，主句要部分倒装，所以排除A,D；C项表示意识到我有多爱他们这一动作发生在left之前，不符合句意，所以选D。