Final answer:
The primary relationship activity in building strategic alliances that encompasses creating possibilities, a shared vision, and the involvement of senior management is 'Imaging'.
Step-by-step explanation:
The primary relationship activity in building strategic alliances that involves seeing the reality in possibilities of an alliance, creating a shared vision from being together, and involving trusted senior managers is known as Imaging. This stage is crucial in promoting a common understanding and ensuring that the senior management is on board, which can help in facilitating a smooth transition into a strategic partnership. It is through Imaging that alliances begin to focus on the potential of their collaboration, taking into account the cultural fit and shared goals necessary for a successful partnership.