那个,“on weekends”是固定词组搭配吗?如果不是,那“weekend”在什么情况下才加S?

那个,“on weekends”是固定词组搭配吗?如果不是,那“weekend”在什么情况下才加S? on weekends 中 weekends 是指几天? 是in weekends 还是on weekends? 是Bob likes going to the movies with his friends on weekends.还是Bob likes to go to the movies with his friends on weekends.那个对? check with 和 check on .那个是固定搭配 on weekends on weekends. 有on the weekends吗一般好像听过on weekends和on the weekend是________the weekends呢?at? 英语中是in the morning on weekends 还是on the morning on the weekends? 在周末英语怎么说是on weekends还是at weekends.在工作日是on weekdays吗? sandy often cleans her room on weekends对划线部分提问划线是on weekends on the weekend ,on weekends at the weekend ,at weekends 分别表示某个固定的周末和一般性的每个周末.怎么理解这些 是on the weekends还是at she weekends详细和为什么 到底是on weekends还是at weekends比如：It's quiet there_________weekends. 是in the weekends还是on the weekends我不确定,但是要写作文.麻烦帮帮忙. on weekends是什么意思 on weekends是什么时态 on the weekends 翻译