Only when I left my parents for Italy how much I loved them.
A. I realized
B. I had realized
C. had I realized
D. did I realize
网友回答
A. I realized
B. I had realized
C. had I realized
(答案→)D. did I realize
解析：考查倒装句。Only +状语/状语从句提前，主谓应用部分倒装。故排除A和B，有根据前面的left，可知本句应是过去时。