Not until yesterdaythat I had made a serious mistake.A. didn’t I realizeB. did I realizeC

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。