Not until I pleted the form that half questions were not relevant to me.
A. had I realized
B. I had realized
C. I realized
D. did I realize
网友回答
A. had I realized
B. I had realized
C. I realized
(答案→)D. did I realize
解析：选D。考查倒装。含有否定意义的词never, seldom, little, hardly, not, scarcely, nowhere, by no means等置于句首时, 句子使用部分倒装语序, 故选D。A项时态错误, 故被排除。