What action signifies the final communication transfer before control is handed off to another controller?

The correct choice, "Transfer Radio Communications," signifies the final communication transfer before control is officially handed off to another controller. This action encompasses the moment when the current controller passes on all relevant information, including the flight's current status and any instructions that the new controller will need. It emphasizes the formal and deliberate exchange of responsibilities, ensuring that the pilot is fully briefed and that all necessary communication protocols are followed so that the transition between controllers is seamless.

In contrast, while terms like "Final Contact," "Handoff Completion," and "Notification of Handoff" may relate to the process of transferring air traffic control duties, they do not encapsulate the definitive action of transferring radio communications which confirms the new controller is now in charge. Each of those terms may describe different points in the handoff process rather than the actual transfer of communication that signifies a completed transition of control.