Question

【题目】The bell rang ______ the teacher was explaining the problem to the students..

A. after B. while C. before

Answer 1

【答案】B

【解析】

试题分析：句意：正当老师向学生们解释这个问题时，铃响了。A. after在……之后；B. while当……的时候；C. before在……之前。只有while能与进行时态连用。故答案为B。