I failed in the spoken examination last term and only then the importance of practicing speaking English.
A. I had realized
B. had I realized
C. I did realize
D. did I realize
网友回答
A. I had realized
B. had I realized
C. I did realize
(答案→)D. did I realize
解析：本题考查倒装。首先由时间状语then确定时态为一般过去时，而时间状语由only引出放于句首，句子产生部分倒装，即助动词提前到主语之前，其他成分保持位置不变。