Is this your sister?
Yes, it is./No,it isn’t.
这里回答用代词it, it不是指的动物吗?是否可以用she?
①is this your sister?
改为陈述疑问句:this is your sister?,所以回答时,it形式主语指代this。
省略版:yes,it is=this is
完整版:yes,it is my sister=this is my sister
还有比如:is this your pen?yes,this is.
②is she your sister?
这时候由it换成了she,所以回答是:
yes,she is./yes she is my sister.