In an exam paper, the following question confused me:

>  - Is this your mother?
>    
>  - No, ***it*** isn’t.

 "your mother" is a lady, how can we use "it" here ?

I wonder whether the following two negative answers is correct or not:

 - No, ***this*** isn't .
 - No, ***she*** isn't.

   How to use the personal pronoun when I answer"Is this..." ?