What action must be completed before an aircraft enters the receiving controller's airspace after a handoff?

The correct answer emphasizes the importance of communication protocols in air traffic control (ATC) during a handoff process. Before an aircraft enters a new controller's airspace, it is essential that radio communications are transferred. This ensures that the receiving controller has established communication with the aircraft, enabling them to provide necessary instructions and information as the aircraft enters their airspace.

Transferring radio communications allows the new controller to assess the aircraft's situation, confirm its intentions, and address any potential issues before they enter the controlled airspace. This step is crucial for maintaining safety and efficiency in busy airspace, as it enables the receiving controller to take responsibility for the aircraft's guidance and to coordinate its sequence with other traffic.

The other choices, while related to the ATC handoff process, do not specifically address the critical need for establishing communication. For example, transferring control involves the physical responsibility for the aircraft, which follows the transfer of communications, while implementation of procedures and a final check, although important, are not the immediate actions required for communication confirmation.