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：考察主谓倒装结构，根据上文可知下文叙述的是过去的事情，故用过去时态，选D，直到我离开父母去意大利时，我才意识到我是多么爱他们。