Question

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

Answer 1

B

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。