The reason he refused to attend the meeting was that they didn’t give him an invitation e

问题补充：

The reason he refused to attend the meeting was that they didn’t give him an invitation earlier.

A. how

B. which

C. why

D. because

答案：

A. how

B. which

(答案→)C. why

D. because

解析：考查定语从句。句中先行词为the reason，在定语从句中作原因状语，故用关系副词why，选C。