he had worked hard all the time he failed the exam again. A. IfB. AsC. WhileD. Because

问题补充：

he had worked hard all the time, he failed the exam again.

A. If

B. As

C. While

D. Because

答案：

A. If

B. As

(答案→)C. While

D. Because

解析：连词辨析。While有一特特殊用法，=though。结合句意可知C正确。句意：尽管他一直很努力，但是他又一次考试不及格。