Only after I read the book why she devoted all her life to medical work forChinese women

问题补充：

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

答案：

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。