That's his pencil--box(복수 형식 이 어야 함)

That's his pencil--box(복수 형식 이 어야 함)

These're their pencil-boxes
That's his pencil-boxes.
pencil-box 만 복수 로 바 꾸 면:
Thoese are his pencil-boxes.
문장 전 체 를 복수 로 바 꾸 면:
Thoese are their pencil-boxes.
Those are his pencil-boxes.
Those are their pencil-boxes.
Those are their pencil -boxes.
That are his pen--boxes.