is this your pen? 为什么答案上面是 yes this is 怎么不用yes it is ...

Is this your pen ? 答案是 Yes , it is.为什么No,it isn't.不对?谢谢 is this( )Japanese pen?yes,it is Is this your son?答案是Yes,he is.还是Yes,it is. Is this your pen?Yes,___(thank). -Is this your pen?-Yes,-----------(thank) is this your pen?----yes,it's. 改错 Is your pen?—Yes,it is.不能用Yes,this is. 为什么Is this your brother?回答是yes,it is 不是yes he is. Is this your brother?Yes,it is.请问这句中为什么用it,而不用he? Is this gutar your Yes,it is( ) Is this your book?Yes,it is Is this Jim?怎么回答yes,he is;Yes,it is.;Yes,this is.