Which of the following statements about the M249 is true?

The M249 is indeed a gas-operated, air-cooled, fully automatic machine gun, which makes this statement accurate. This firearm is specifically designed to provide sustained fire support and is capable of firing continuously as long as ammunition is available and the trigger is held down.

The M249 uses a piston system that harnesses gas from fired cartridges to cycle the action, which distinguishes it from other weapon types. Being air-cooled is essential for machine guns as it allows them to manage heat during extended firing sessions. The fully automatic capability means that the weapon can fire multiple rounds with a single pull of the trigger, allowing for rapid suppression of enemy positions.

Understanding the operating principles of the M249 helps highlight its functionality as a support weapon on the battlefield, tailored for infantry units needing an efficient means to deliver sustaining fire.