Explanation: Enhanced Group Calls (EGC) are a crucial component of the Global Maritime Distress and Safety System (GMDSS) for broadcasting maritime safety information (MSI), such as navigational warnings, meteorological warnings, and search and rescue information, to groups of ships in specific geographical areas. EGCs are transmitted over the **Inmarsat satellite** system (D). Specifically, the Inmarsat-C system provides the SafetyNET (for MSI) and RescueNET (for SAR) services which utilize Enhanced Group Calls to target vessels. Inmarsat offers reliable, global satellite coverage (excluding the extreme polar regions), making it ideal for broadcasting critical safety information far offshore. COSPAS-SARSAT (A) is a satellite system dedicated to detecting distress alerts from EPIRBs, ELTs, and PLBs, not for broadcasting MSI. HF SITOR (NBDP) shore stations (B) and NAVTEX shore stations (C) are terrestrial systems primarily operating on HF or MF frequencies respectively. While both contribute to MSI dissemination, they are distinct from the satellite-based EGC service.