What element of a shotgun is responsible for storing cartridges?

The magazine is the component of a shotgun that is specifically designed to store cartridges until they are ready to be fed into the chamber for firing. In shotguns, the magazine can be either an internal part of the firearm or an external removable part, depending on the design of the shotgun. This storage capability allows for quick reloading and facilitates multiple shots in a short period, which is especially useful in hunting and shooting sports.

The action of a shotgun refers to the mechanism that loads, fires, and ejects shells. The trigger is the lever that initiates the firing mechanism when pulled, and the muzzle is the end of the barrel from which the shot exits. While all these parts are essential for the functioning of a shotgun, only the magazine is specifically meant for holding cartridges, making it the correct answer in this context.