Which parts make up the three major components of a firearm?

The three major components of a firearm are correctly identified as the stock, action, and barrel.

The stock is the part of the firearm that you hold and provides stability when aiming and firing. It supports the action and the barrel and is often made of wood or synthetic materials. The action is the mechanism that loads, fires, and ejects cartridges, and can be one of several types, such as bolt-action or semi-automatic. The barrel is the metal tube through which the bullet travels when fired, and it also plays a crucial role in determining the accuracy and velocity of the projectile.

Each of these components is essential for the function of the firearm. While other parts like the trigger or magazine are important, they do not make up the three major components as defined in this context. Thus, choosing the stock, action, and barrel encompasses the primary functioning elements of a firearm, making this answer the most accurate option.