Explanation: VHF radios with Digital Selective Calling (DSC) store the Maritime Mobile Service Identity (MMSI) in non-volatile memory. This is a critical safety feature, as the MMSI is a unique identifier for a vessel and is used for distress and routine calls. To prevent accidental or unauthorized changes that could compromise maritime safety and emergency response, most manufacturers implement a system where the MMSI can typically only be programmed once by the user. If a new MMSI is required (e.g., due to a change of vessel ownership or the radio being moved to a new vessel), the existing MMSI memory usually needs to be cleared by the manufacturer or an authorized service center. They possess the necessary tools or software to perform this reset. * **A) You must RESET the DSC memory...**: User-accessible resets usually clear settings or call logs, not the fundamental MMSI, which is often protected against casual changes. * **B) You can never change a number...**: This is incorrect. While a user typically cannot, the manufacturer or an authorized service center often can. * **C) Re-register the old MMSI with the new owner...**: This is improper. Each MMSI is unique and tied to a specific vessel. If the radio is on a different vessel or ownership has changed, a new MMSI should be registered for the *current* vessel, and the radio must reflect that correct, unique identifier.