Explanation: Radiocommunication protocols establish a strict hierarchy of message priority to ensure the most critical communications are handled first. **Distress** (signified by MAYDAY) indicates grave and imminent danger to a vessel, aircraft, or person, and requires immediate assistance. This is the absolute highest priority. All other transmissions must cease immediately. **Urgency** (signified by PAN-PAN) indicates a very urgent message concerning the safety of a vessel, aircraft, or person, but it does not signify immediate grave danger requiring distress-level intervention. While urgent, it is secondary to a Distress situation. Therefore, **Distress** has a higher priority than Urgency. **A) Ship-to-ship routine calls** are general communications and have the lowest priority, requiring cessation for any emergency traffic. **C) Safety** (signified by SÉCURITÉ) conveys important navigational or meteorological warnings. It is lower in priority than Urgency. The established hierarchy is Distress > Urgency > Safety. **D) Security** is not a specific priority signal within this international framework; general security communications would be routine or lower priority.