What type of association does an ARC organization have when it has principal responsibility for a weapon system shared with regular organizations?

An ARC organization exhibiting a principal responsibility for a weapon system that is shared with regular organizations exemplifies an Active Association. In this context, an Active Association indicates that the ARC (Acquisition Resource Center) organization not only plays a central role in the management and oversight of the weapon system but also actively engages in its development, maintenance, and operational integration with the regular organizations. This type of association suggests a high level of collaboration and responsibility, which is essential for ensuring that all stakeholders are aligned and that the weapon system is effectively utilized.

The other options represent different forms of associations but do not convey the same level of responsibility as seen in an Active Association. For example, Classic Association may involve more traditional roles without the principal oversight aspect, Joint Association often pertains to collaborations between different entities or branches rather than a singular focus on operational management, and Collaborative Association suggests teamwork without the emphasis on principal responsibility that Active Association captures. Thus, Active Association accurately describes the relationship delineated in the question.