Replace the possessive noun or noun phrase with the correct pronoun

Beth's books.

Billy's ball.

The chicken's eggs.

Rover's bone.

What is a pronoun? Him, her, they, them, etc.

Whose books are they? They're hers. Her books.

Whose ball is it? It's his. His ball.

The chicken's gender isn't revealed so the pronoun is it. Its eggs. No apostrophe.

Rover is likely a boy dog, so it's the same as Billy's ball.