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 give him an invitation earlier.

A. how

B. why

C. which

D. that

答案：

A. how

(答案→)B. why

C. which

D. that

解析：句意，他们拒绝参加会议的原因是因为他们没有提前向他发出邀请。根据前置词the reason可知引导词需用why为什么。故选B。