Is it a circle?
Yes, it is.
Is it a circle?
No, it isn't.
Is it a square?
Yes, it is.
Is it a square?
No, it isn't.
Is it a triangle?
Yes, it is.
Is it a triangle?
No, it isn't.
Is it a rectangle?
Yes, it is.
Is it a rectangle?
No, it isn't.
It ( is / isn't ) an eraser.
is
It ( is / isn't ) a pen?
isn't
It ( is / isn't ) a desk.
isn't
It ( is / isn't ) a notebook.
is
