What are the three main parts of a shotgun?

The three main parts of a shotgun are indeed the barrel, stock, and receiver. The barrel is the long metal tube through which the shot or bullet travels when the shotgun is fired; its design influences the accuracy and range of the firearm. The stock is the part of the shotgun that is held against the shoulder, providing stability and aiding in recoil management during firing. The receiver is the central part of the shotgun that houses the operating mechanism and integrates the components that facilitate loading, firing, and ejection of shells.

Understanding these components is crucial for both safe handling and effective use of shotguns. The other options do mention some components found in shotguns; however, they do not encompass the essential parts that collectively define the firearm's main structure and function.