Question

–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

Answer 1

C

试题分析：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。