题目内容
The students _______ their homework carefully when the teacher walked into the classroom quietly.
A. doB. did
C. are doing D. were doing
D
【解析】
试题分析:句意:学生们正在认真做作业,当老师安静地走进教室时。根据when the teacher walked into the classroom quietly当老师安静地走进教室时,可知学生们正在做某事,从句为一般过去时,主句为过去进行时,故选D.
考点:考查过去进行时
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