Yesterday I happened to see John Mike, ( ) was eager to have a

Yesterday I happened to see John Mike, ( ) was eager to have a talk with you.
A、that
B、which
C、who
D、whom
【正确答案】：C
【题目解析】：who 引导的定语从句，且在定语从句中做主语，句子含义为昨天我见到了麦克，他特别想和你聊天。