Only after I read the book why she devoted all her life to medical work for
Chinese women and children.
A. I understood
B. had I understood
C. did I understand
D. I had understood
网友回答
A. I understood
B. had I understood
(答案→)C. did I understand
D. I had understood
解析： 考查倒装句.以only开头的句子,主句用部分倒装.句意,我读了这本书后,明白了她为什么……，可知主句表述的是过去发生的动作，故用过去时态，选C。