How is a Distress priority message ordinarily initiated on board the vessel?

Correct Answer: Option B — By pressing one or more dedicated "Distress key" on the equipment.

GMDSS equipment, including Inmarsat terminals, must feature a dedicated Distress button to minimize human error during emergencies. This button triggers the transmission of a pre-formatted Distress alert containing the vessel's identity, position, and nature of distress, ensuring immediate recognition and priority handling by the Land Earth Station.