Which of Newton's laws is being explained?

Question

A bumper accelerates and hits a second bumper car at rest. The second bumper car begins to slide.

Answer 1

This scenario is an example of Newton's third law of motion: for every action, there is an equal and opposite reaction. When the first bumper car accelerates and hits the second car, the force exerted by the first car on the second car causes the second car to move in the opposite direction.