Question

My father was preparing for his speech __ my mother was doing some washing last night.

A．if

B．while

C．unless

D．until

Answer 1

B

考查时间状语从句。句意“昨晚我爸爸正在为演讲做准备，而妈妈正在洗衣服。”while表对比，前后都用进行时。故选B。