What is the correct sentence?

Question

for an example "this is his book"

and what i want to know it when the "he" becomes "she",what shud be the sentence

A.This is her book

B.This is hers book.

Answer 1

The correct sentence should read - This is - her - book.

Here are other options -

This is hers (referring to the book).

This book belongs to her.

This (referring to the book again) belongs to her.

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Answer 2

A. HER book

Answer 3

A. This is her book