Question

The action and reaction forces referred to in Newton’s third law:

(A)must act on the same object
(B)may act on different objects.
(C)must act on different objects.
(D)need not be equal in magnitude but must have the same direction.

Answer 1

(C) Must act on different objects because shooting a bullet is one example-the action force is on bullet but the reacion force is on the gun and that's why it moves backwards

Answer 2

(C) Must act on different objects is the correct answer.
If action and reaction forces act on the same object, both of them would get cancelled and hence, would result in no motion of the object.
So, it is certainly not "may" but "must".
Action and reaction forces may differ in their magnitudes but are always opposite in direction.
Firing a bullet, breaking of a shell into pieces, a walk on floor and hitting a ball against the wall are a few good example to prove this.