He made three good friends in the university joined the army after graduation.A. one of

问题补充：

He made three good friends in the university, joined the army after graduation.

A. one of them

B. one of whom

C. one

D. one of which

答案：

A. one of them

(答案→)B. one of whom

C. one

D. one of which

解析：考查定语从句。句意：他在大学里面交了三个好朋友，其中之一毕业后参了军。本句先行词three good friends下文逻辑主语，作介词宾语的指人的引导词只能使用whom，故用选B。