It's a book
They're books
They're books
It's a book
They're pencils
It's a pencil
They're pencils
It's a pencil
It's a pen
They're pens
It's a pen
They're pens
It's an eraser
They're erasers
They're erasers
It's an eraser
It's a ruler
They're rulers
They're rulers
It's a ruler
