They started _____ the classroom twenty minutes ago. A. clean B. cleaning C. cleans D. cleaned

分类: 作业答案 • 2021-12-20 02:52:50

问题描述：

答

start doing 开始做某事

答

B “二十分钟前他们开始打扫教室”
start doing sth = start to do sth “开始做某事”