Is this your sister?与Is she your sister?的回答及用法的异同点

Is this your sister ? Yes, this is my sister. No, this isn't. This isn't my sister.
Is she your sister ? Yes , she si my sister. No, she isn't . She isn't my sister.

两者都是问某人是不是你姐姐(妹妹)? "this "用在多人中，靠近被问者的一个而且问者没有把握时；“she”是用在问话者比较肯定的某人时，或者是一男一女时，指着女人问男人时用。

Is this your sister?(她本人可能不在场。以正在看照片时为例）
Yes, it is （It指心目中的人----她）
No, it isn't
Is she your sister?（以真人为背景，她就在那边）
Yes, she is
No, she isn't

Is this your sister?估计这个sister不在场
Yes, it is
No, it isn't
Is she your sister?在场，但是在远处可以看的见的地方
Yes, she is
No, she isn't