Which statement concerning Inmarsat-B and Inmarsat-C terminals is correct?

The correct statement is that Inmarsat-B terminals require AZ/EL setup and gyro input in order to enable automatic satellite tracking. Inmarsat-B terminals are designed to automatically track satellites, which involves determining the appropriate azimuth (AZ) and elevation (EL) angles needed to maintain communication with the satellite. The inclusion of gyro input is critical for the system to accurately understand its own orientation and movement, ensuring that the antenna can adjust dynamically in response to changing satellite positions.

The requirement for AZ/EL setup allows for initial alignment of the terminal, while gyro input provides continuous tracking capability by compensating for any movement or changes in the installation's position. This technical setup is essential for maintaining a stable and effective communication link, especially in maritime environments where conditions can change rapidly.

In contrast, the other options presented do not accurately reflect the technical requirements for automatic satellite tracking by these systems.