Explanation: All Maritime Mobile Service Identities (MMSI) are standardized as 9-digit numbers. These digits are assigned according to international regulations to uniquely identify maritime communication entities. The first three digits of a ship station MMSI, or the digits following leading zeros for other types of stations, are the Maritime Identification Digits (MID), which identify the country of the station's administration. This structure ensures a globally consistent and unique identification system. Option A is incorrect because coast station MMSI numbers begin with two zeros (00), followed by the MID, not with the digit 4. Option C is incorrect as all ship station MMSI numbers are 9 digits; Inmarsat terminals have their own separate identification, which is not an MMSI. Option D is incorrect because group call MMSI numbers begin with a single zero (0), not two zeros.