Which major component of the M500A1 service shotgun contains the safety, ejection port, and fore-end?

The correct answer is the Receiver Group because it serves as the central housing for many critical components of the shotgun. The receiver group contains the mechanism for firing the weapon, which includes the safety, and it also houses the ejection port where spent shells are expelled after firing. The fore-end, often referred to as the forearm, is mounted on the front of the receiver and provides a grip for stabilizing the shotgun when firing. This grouping allows the operator to safely handle the shotgun and provides essential functions for its operation.

In contrast, the other groups have specific roles: the barrel group primarily focuses on directing the projectile, the stock group pertains to the part that interfaces with the user's shoulder for support, and the trigger group is responsible primarily for the firing mechanism but does not encompass safety or ejection components. Thus, the Receiver Group is truly the major component that integrates these functionalities.