the shop closes early on Fridays 里面的Friday为什么要加S?

the shop closes early on Fridays 里面的Friday为什么要加S? The shop o_ early on Fridays. 请问on Friday 和on Fridays的区别是什么呢 on friday afternoon的friday前为什么不加the?告诉我语法就行 什么时候用on fridays什么时候用on friday,他们有什么区别,还有我、在星期五的早晨fridays it was sunday,a never get up early on sundays.sunday为什么要加S I never get up early on Sundays.为什么Sunday后面要加s It's 5 o'clock now,the shop is (A,close B closes,C closed,D The shop sells shoes of all kinds.这里的SELL为什么加S? She is going to the shops?为什么shop后面要加s? 为什么名词所有格有的名词后面要加s,有的后面不要加s 例如 in the shoe shop 为什么是on Friday afternoon而不是in the Friday afternoon