Which two types of weapons can be physically attached to the M16 and M4 rifles?

The correct answer highlights the compatibility of attachment systems used with the M16 and M4 rifles. Both grenade launchers and shotguns are designed to be physically mounted to these rifles, enhancing their versatility in different combat scenarios.

Grenade launchers, such as the M203 or M320, can be directly attached to the underside of the M16 or M4, allowing soldiers to fire grenades in addition to conventional small arms ammunition. This capability expands the firepower available to a soldier without the need to carry multiple separate weapons.

Shotguns can also be attached using various mounting systems. Attaching a shotgun to an M16 or M4 allows for close-quarters engagements with increased effectiveness against certain threats, such as breaching doors or engaging targets at very close range.

In contrast, the other answer choices do not consist of weapon systems that are designed for physical attachment to M16 and M4 rifles. Sniper rifles and light machine guns are typically independent systems that serve different purposes and are not intended to be mounted together. Likewise, submachine guns and pistols generally operate as standalone weapons. Finally, launchers and missile systems, while critical in combat, do not physically attach to the M16 or M4 in the manner that grenade launchers