A book weighing 10 N rests on a table. There is a normal force n acting upwards on the book, and the
weight, W, of the book acts downwards. Since n is equal and opposite to W, we (can)/(cannot) say
that n and W comprise an action-reaction pair. The reason is because action and reaction pairs always
(act on the same object) (act on different objects), and here we see n and W (both acting on the apple)
(acting on different objects).