Answer:

a. When the person sitting in a rolling chair pushes on the desk, this push or force is the action force. Now, the desk pushes back against the person with a force of the same size. This reaction force will cause the rolling chair to move backwards. Notice that the two forces act on different objects.

b. The engine provides the force to turn the tires which, in turn, pushes backwards against the road surface. By Newton's Third Law, the "reaction" of the surface to the turning wheel is to provide a forward force of equal magnitude to the force of the wheel pushing backwards against the road surface.

Explanation:

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