Which scenario is an example of Newton's third law of motion?

Newton's third law of motion states that for every action, there is an equal and opposite reaction. In the scenario of a diver pushing off a diving platform, the action is the diver applying a force against the platform. In response to this force, the platform exerts an equal force back on the diver, propelling them upward into the air. This interaction exemplifies the principle that forces always come in pairs; the diver's push against the platform results in a movement away from the platform due to the reaction force.

In contrast, the other scenarios do not illustrate this law as clearly. A car accelerating down a highway primarily demonstrates the relationship between force and mass (Newton's second law) rather than the action-reaction principle. A stationary basketball on the court reflects Newton's first law of motion, as it remains at rest until acted upon by an external force. A runner maintaining a constant speed is indicative of balanced forces, again relating more to first law concepts rather than the direct action and reaction described in Newton’s third law.