— I rang you at about nine but there was no reply.— Oh that was probably I was seeing th

问题补充：

— I rang you at about nine, but there was no reply.

— Oh, that was probably I was seeing the doctor.

A. why

B. when

C. what

D. That

答案：

A. why

(答案→)B. when

C. what

D. That

解析：句意：--昨晚我打电话给你,但是没有人接电话。--哦，那很有可能我正在看医生。依据上下文was后应是表时间的表语从句，只能用when来引导。

考点: 考查表语从句关系词的用法。