Final answer:
The principal air and space force of the United States is the U.S. Air Force (C). Established as an independent military branch after WWII, its main tasks include aerial, space, and cyber warfare. The President serves as Commander in Chief over all branches, including the Air Force.
Step-by-step explanation:
The United States' principal air and space force is the U.S. Air Force. The Air Force was established as a separate branch of the military after World War II. Following the National Security Act of 1947, it became an independent service, distinct from the U.S. Army, separating the Army's aerial division from its ground forces. The Air Force's primary responsibilities include aerial warfare, space warfare, and cyber warfare. As such, the correct answer to the question of which military service is the United States' principal air and space force is C. Air Force.
It is important to note that the United States Armed Forces consists of the Army, Navy, Marine Corps, Air Force, and the Coast Guard. Each branch has a unique role, and the President of the United States serves as the Commander in Chief, ensuring that the military remains under civilian control, as stated in Article 2 of the Constitution.