问题补充:
Not until yesterdaythat I had made a serious mistake.
A. didn’t I realize
B. did I realize
C. I didn’t realize
D. I realize
答案:
A. didn’t I realize
(答案→)B. did I realize
C. I didn’t realize
D. I realize
解析:选B。考查倒装语序。not until接状语从句放在句首时, 主句用倒装结构。