Explanation: Sending a brief test message to your own Inmarsat-C terminal (or a registered address associated with it) is the easiest and most comprehensive test. This action confirms the entire communication chain: your terminal's ability to transmit, the satellite link, the land earth station (LES) processing, and your terminal's ability to receive. It verifies the functionality of the transmitter, receiver, antenna, and the network registration without involving external parties or burdening emergency services. Options B and C are inappropriate as they would involve unnecessary communication with RCCs (Rescue Coordination Centers) or other vessels, which should be reserved for safety-related or urgent traffic. Option D, using an internal POST (Power-On Self-Test), only checks the terminal's internal hardware and software; it does not verify the RF components (transmitter/receiver), antenna, or connectivity to the satellite network.