Do you know the reason he was late?A. for whichB. for whatC. whichD. that

问题补充：

Do you know the reason he was late?

A. for which

B. for what

C. which

D. that

答案：

(答案→)A. for which

B. for what

C. which

D. that

解析：本题考查定语从句。the reason后接定语从句，如从句意义完整，引导词用作状语的why或for which。