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