Which of the following describes the operation of the .50 caliber machine gun?

The .50 caliber machine gun is classified as a fully automatic firearm. This means that once the trigger is pulled, the weapon will continue to fire rounds as long as the trigger remains depressed. This design allows for rapid and sustained fire, making it highly effective in military engagements.

In contrast, other types of operations noted in the options do not accurately describe the .50 caliber machine gun's functioning. Semi-automatic refers to a firearm that fires one round with each trigger pull, requiring a new trigger pull for each shot. Lever-operated and pump-action firearms also fall into categories that require manual cycling of action, which does not apply to the continuous firing capability of a fully automatic machine gun. Thus, the classification as fully automatic is essential to understanding the operational characteristics of the .50 caliber machine gun.