Which of the following is a term that refers to the Army, Navy (including Marine Corps and Coast Guard), and the Air Force?

The term that refers to the Army, Navy (including Marine Corps and Coast Guard), and the Air Force is "Military Department." This designation is used to categorize the individual branches of the U.S. Armed Forces, each of which has its own Department within the Department of Defense. These military departments include the Department of the Army, the Department of the Navy, and the Department of the Air Force. Each military department is responsible for organizing, training, and equipping forces and executes its functions and missions within its specific service area.

Other terms, such as "Joint Forces," indicate collaborative operations among the different military branches but do not singularly represent them. "Combined Forces" typically refers to military operations that involve forces from multiple nations working together, rather than solely from the U.S. branches. "Unified Combatant Command" denotes a unified command structure that encompasses multiple service branches, often for specific operations or geographic areas, but it does not define the individual departments themselves. Thus, "Military Department" accurately captures the essence of the Army, Navy (including Marine Corps and Coast Guard), and Air Force as distinct yet integrated branches within the U.S. military framework.