Explanation: A nine-digit MMSI (Maritime Mobile Service Identity) beginning with a single "0" (e.g., 0MIDXXXXX) indicates a Group Call MMSI. This special type of MMSI allows a single digital selective calling (DSC) transmission to be addressed to multiple ships simultaneously, useful for fleets, convoys, or organizations. A single ship station MMSI typically begins with a Mobile Identity Digit (MID) from 2-9 (e.g., 366xxxxxx for a US ship). A coast station MMSI starts with two zeros (00MIDXXXX). While Inmarsat-C terminals have IDs, their structure doesn't align with this specific MMSI format.