In what type of association does a Regular Air Force organization retain principal responsibility for a weapon system shared with ARC organizations?

The correct answer is Classic Association. In a Classic Association, the Regular Air Force organization maintains principal responsibility for managing and operating a weapon system while sharing it with Air Reserve Components (ARC) organizations. This type of association allows for a clear delineation of responsibilities, ensuring that the Regular Air Force's expertise and leadership are central to the operation of the weapon system.

This structure effectively combines the strengths of both Regular and Reserve components, permitting an integrated approach to managing personnel, equipment, and resources while maintaining operational readiness and efficiency. In this arrangement, while the ARC contributes to the overall mission, the Regular Air Force retains the primary oversight and operational control, fostering collaboration and ensuring that the systems are effectively utilized and maintained.

Other associations like Active and Cooperative differ in how responsibilities are shared and managed, often leading to less clarity in command or operational control compared to the Classic Association model.