Do you know the reason he was late for the class?A. whyB. thatC. whichD. who

问题补充：

Do you know the reason he was late for the class?

A. why

B. that

C. which

D. who

答案：

(答案→)A. why

B. that

C. which

D. who

解析：考查定语从句。先行词为表示原因的单词the reason，故引导词只能使用why为什么，选A。