Which of the following describes a key feature of the M16A2E3?

The M16A2E3 is a variant of the M16 rifle series and is notable for its capability to fire in both semi-automatic and fully automatic modes, making it versatile in various combat situations. This feature allows the user to choose between firing single shots for precision or automatic fire for a higher rate of fire when needed, showcasing the adaptability required on the battlefield.

This dual functionality enhances the effectiveness of the rifle in different tactical scenarios, such as engaging distant targets with precision or suppressing enemy positions with sustained fire. The other options do not correctly represent the characteristics of the M16A2E3 or its intended use in combat, which further highlights why the identified capability is a key feature of this firearm.