Newton's 3rd Law of Motion states that for every action, there is an equal and opposite reaction. This means that whenever an object exerts a force on another object, the second object exerts a force of equal magnitude in the opposite direction on the first object. Let's examine the given options to determine which ones demonstrate this law:

a) Recoil of a gun:
- When a gun is fired, the bullet is propelled forward with a certain force.
- According to Newton's 3rd Law, the gun experiences an equal and opposite force, causing it to recoil backward.
- This demonstrates the action-reaction pair of forces acting between the gun and the bullet.

b) Motion of a rocket:
- Rockets work on the principle of action and reaction.
- The rocket engines expel gases with a high velocity in one direction (action).
- As a result, the rocket experiences a force in the opposite direction (reaction) that propels it forward.
- This exemplifies Newton's 3rd Law as the action of expelling gases leads to the reaction of the rocket's motion.

c) Swimming:
- Swimming involves the movement of a person through water by exerting force against it.
- When a swimmer pushes against the water with their arms and legs, the water exerts an equal and opposite force on the swimmer.
- This force helps propel the swimmer forward, demonstrating Newton's 3rd Law.

d) All of the above:
- As explained above, both the recoil of a gun, the motion of a rocket, and swimming involve the application of Newton's 3rd Law of Motion.
- In all these cases, an action force is exerted, and an equal and opposite reaction force is experienced.

In conclusion, all of the given options (a, b, and c) are examples of Newton's 3rd Law of Motion, as they demonstrate the concept of action and reaction forces.