This is the reason he was late for class today.A. whyB. for thatC. whichD. that

问题补充：

This is the reason he was late for class today.

A. why

B. for that

C. which

D. that

答案：

(答案→)A. why

B. for that

C. which

D. that

解析：句意：这就是他今天上班迟到的原因。先行词是the reason的时候，而且定语从句中不缺主宾表，用why引导定语从句，所以选A。