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We couldn't watch until our homework was finished.

来源:学生作业帮 编辑:作业帮 分类:英语作业 时间:2024/10/03 06:44:56
We couldn't watch until our homework was finished.
为什么用couldn't 换成cann't 行不行 could 和 can 有什么区别?
区别在于语气和事态两种情况
语气上couldn't比can't委婉点 客气点
时态上couldn't是can't的过去形式
你是句话属于后者 因为后面有was 所以为了时态一致要用couldn't