this is not,this's not,this isn't哪个正确哪个正确呢?怎么会这样?为什么单单那个不可以

this is not will`s is this ( ) watch no,it's not ( ) this S/N is not available.Please check if it is the right one.中文是什么 this is a event of this product s/n this is not this is not Is not this this is not a this.is.not.a. This is not Mary's dress.(变为一般疑问句） This question is not difficult. It's very s______. 这个句子对不对：This bag is not Tom's. This is my new b .It's not very b , 补全对话 This is Liu Ling.I ( )this morning,but he's not in. IS this your cup?NO,it's not mIS this your cup?NO,it's not m______? this card is not available This Is Not Love 歌词 This Site Is Not Exit!