These are your book和These are your books都是一个意思,为什么一个有s一个没有s?

These books are 是yours还是your 是Mary ’ book还是Mary ’s Are they your books?还是Are these your books?为什么? These are your book's ,aren't they和Those aren't your pens,ar John,are these books----(your) these are (they)books.those are (your) what nationality are you和what’s your job都是''你''的为什么一个用are一个用 are these your books?改为单数形式 These are your books.变一般疑问句 Are these your books?肯定回答 Are these your books?作否定回答 Are these your books?的否定回答 These are------------ your books中间是什么