Explanation: The Global Maritime Distress and Safety System (GMDSS) is an internationally agreed-upon set of procedures, equipment, and communication protocols designed to enhance safety at sea and facilitate the rescue of ships in distress. GMDSS achieves its objectives by integrating various communication technologies: * **Alerting Shore-based Authorities (Option B):** Systems like EPIRBs, Digital Selective Calling (DSC), and satellite communications (Inmarsat) are designed to rapidly alert Search and Rescue (SAR) coordination centers ashore about a distress situation. * **Alerting Nearby Shipping (Option C):** DSC and satellite communications also enable the rapid alerting of vessels in the immediate vicinity of a ship in distress, allowing them to provide assistance quickly. * **Coordinated SAR Operations (Option A):** By simultaneously alerting both shore authorities and nearby ships, GMDSS ensures a comprehensive and coordinated response, minimizing delays in SAR operations. This multi-faceted approach allows for the most efficient use of resources, whether from dedicated SAR assets ashore or vessels already in the area. Therefore, the basic concept of GMDSS encompasses all these elements to create a robust and interconnected safety network for the maritime community.