What do they often do on Sundays.为什么这个句子的Sunday要加s?可有些句子没加s?
问题描述：
What do they often do on Sundays.为什么这个句子的Sunday要加s?可有些句子没加s?
答
因为不是单指某一个sunday啊,它是指通常的情况下里的sunday,就不是指一个sunday啦