Whose dog is this?
It's Susan's dog.
Whose books are these?
They're Mark's books.
Whose cat is this?
It's Mark's cat.
Whose dress is this?
It's Susan's dress.
Whose apple is this?
It's Susan's apple.
Whose doll is this?
It's Susan's doll.
Whose crayons are these?
They're Mark's crayons.
Whose cap is this?
It's Mark's cap.
Whose glasses are these?
They're Mark's glasses.
Whose ball is this?
It's Mark's ball.
Whose rulers are these?
They're Susan's rulers.