It's a ruler / book.
book
It's a sharpener / ruler.
ruler
It's a book / schoolbag.
schoolbag
It's a sharpener / pencil case.
pencil case
It's a rubber / ruler.
rubber
It's a rubber / sharpener.
sharpener
It's a pen / penci case.
pen
It's a pencil / pen.
pencil