His father often comes back from work at 10 o’clock at night his mother is waiting for hi

His father often comes back from work at 10 o’clock at night his mother is waiting for him.
A. that
B. when
C. where
D. which

A. that (答案→)B. when C. whereD. which解析：考查定语从句。定语从句的先行词是指代时间的10 o’clock，定语从句的结构很完整，故使用关系副词when。句意：他的父亲常常在晚上10点回家，在那时他的妈妈正在等着他。故B正确。

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