问题
选择题
–When did he come back last night?
--It was at 8 o’clock ________ I was watching a documentary on TV.
A．since
B．that
C．when
D．which
答案
答案：C
题目分析：考查定语从句。句中先行词为8 o’clock，在定语从句中作时间状语，故用关系副词when。句意：——昨晚他什么时候回来的？——8点钟，当时我正在看一部电视纪录片。故C正确。