Which of the following is NOT one of the Air Force Core Functions?

The correct answer highlights that "Cyber defense" is not classified as one of the Air Force Core Functions. The Air Force identifies several core functions that encapsulate its primary missions, and these include air superiority, global strike, and rapid global mobility.

Air superiority ensures control of the airspace, providing a crucial advantage in both offensive and defensive operations. Global strike represents the Air Force's capability to project power globally with precision and speed. Rapid global mobility emphasizes the swift transportation of forces and materials anywhere in the world, enabling immediate response to threats and contingencies.

While cyber defense is undoubtedly a vital aspect of modern military operations and is encompassed under broader cyber capabilities and operations, it does not fall under the designated core functions of the Air Force. Thus, selecting cyber defense as the answer correctly identifies it as outside that core function framework.