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
网友回答
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。