Which law states that for every action, there is an equal and opposite reaction?

The law that states that for every action, there is an equal and opposite reaction is Newton's third law. This principle highlights that forces always occur in pairs. When one object exerts a force on another object, the second object exerts a force of equal size but in the opposite direction on the first object. This can be commonly observed in various scenarios, such as when you push against a wall, and the wall pushes back with an equal force.

Newton's first law, often referred to as the law of inertia, states that an object in motion will stay in motion unless acted upon by a net external force, focusing on the behavior of objects at rest or in uniform motion. Newton's second law provides the relationship between force, mass, and acceleration, encapsulated in the formula F=ma, which describes how the velocity of an object changes when it is subjected to an external force. Newton's law of universal gravitation describes the attractive force between two masses, indicating how gravity works on a universal scale.

Therefore, the correct identification of Newton's third law emphasizes the importance of action-reaction pairs in understanding the fundamental interactions in physics.