Only when he saw the test paper himself he had failed in the exam again.A. he believedB.

问题补充：

Only when he saw the test paper himself, he had failed in the exam again.

A. he believed

B. he had belived

C. did he believe

D. had he believe

答案：

A. he believed

B. he had belived

(答案→)C. did he believe

D. had he believe

解析：考查only+时间状语从句，后面的主句用部分倒装，句意：只有当他看见考试卷，他才相信考试有没及格。可知要用过去时，选C。