Which of the following is a characteristic of the M60 machine gun?

The M60 machine gun is characterized by being air-cooled and belt-fed, which makes it suitable for sustained fire in combat situations. The air-cooling system allows for rapid heat dissipation, which is essential for maintaining performance during prolonged engagements. The belt-fed mechanism enables a continuous supply of ammunition, allowing the operator to engage targets without the need for frequent reloading, which is critical during intense firefights. This combination of features contributes to the M60's effectiveness as a light machine gun, making it a valuable asset for infantry units.

The other options describe characteristics that do not align with the M60's design and function. The M60 is not a bolt-action rifle, it does not utilize a detachable magazine, and it does not use 5.56mm ammunition; instead, it is designed to fire 7.62mm NATO cartridges, further distinguishing its capabilities in the battlefield.