He changed so much that only when I looked closely he was exactly my long lost friend.
A. I realized
B. did I realize
C. I did realize
D. realized I
网友回答
A. I realized
(答案→)B. did I realize
C. I did realize
D. realized I
解析：B 考查倒装句。Only 修饰状语when I looked closely，后面的主句要部分倒装，把助动词did提前，因此选B。