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