Final answer:
The MMSI number serves as a unique identifier for maritime communication systems and consists of 9 figures. Option A is the correct choice.
Step-by-step explanation:
The purpose of the MMSI number (Maritime Mobile Service Identity) is to provide a unique identifier for maritime communication, particularly for the use of digital selective calling (DSC), automatic identification systems (AIS), and certain types of satellite communications. An MMSI number is composed of 9 figures, which makes option A the correct choice: Maritime Mobile Service Identity; 9 figures.