Which major component group consists of the cartridge extractor, ejector, and firing pin?

The Bolt Carrier Assembly is the correct choice because it houses essential components that are critical to the firing and cycling process of the weapon. Within this assembly, the cartridge extractor is responsible for gripping and pulling the spent cartridge case from the chamber after a round has been fired. The ejector also plays a vital role, as it works in conjunction with the extractor to ensure that the spent casing is ejected from the firearm, preventing any potential jams that could occur during cycling. Additionally, the firing pin, which strikes the primer of the cartridge to initiate combustion, is also part of this assembly. This assembly’s design and functionality are crucial for the overall operation of the M16A3/M4A1, ensuring reliable firing and ejection of spent cartridges.

In contrast, the Upper Receiver Assembly contains the barrel and bolt carrier, but does not house the extractor, ejector, or firing pin itself. The Buttstock is primarily concerned with the stability and support of the rifle and does not contain any of the listed components. The Magazine Group Assembly is responsible for feeding ammunition into the chamber but does not include components directly involved in the firing process.