He was busy writing the exam paper, only ___once in a while to check the time. A. to stop B. stoppin...
2022-10-15 21:41:25 64次 2015-2016学年广东汕头金山中学高二下期中考试英语卷（解析版） 单项填空 反馈错误 加入收藏 正确率 : 100%
题目内容：
He was busy writing the exam paper, only ___once in a while to check the time.
A. to stop B. stopping
C. to have stopped D. having stopped
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