Question

【题目】The students were singing an English song _______ Mr. Jackson came into the classroom.

A. while B. when C. before D. as

Answer 1

【答案】B

【解析】试题分析：句意：当向老师进入教室时，学生们正在唱一首英语歌曲。When引导的时间状语从句用一般过去时，主句用过去进行时，故选B。