Is this the reason at the meeting for his carelessness in his work?A. why he explained B.

问题补充：

Is this the reason at the meeting for his carelessness in his work?

A. why he explained

B. what he spoke

C. he explained

D. he spoke

答案：

A. why he explained

B. what he spoke

(答案→)C. he explained

D. he spoke

解析：he explained前省略了that,reason后跟了一个定语从句。