Explanation: MF-HF SSB transmitters are ideal for simultaneous long-range GMDSS communications because MF-HF frequencies support reliable long-range propagation via groundwave and skywave, crucial for reaching distant RCCs, coast stations, and SAR assets in Sea Areas A2, A3, and A4. Single Sideband (SSB) provides voice communication, enabling real-time, dynamic coordination and information exchange among multiple parties (distress vessel, SAR aircraft, OSC vessels, RCC). This direct, simultaneous voice interaction is critical during a fast-evolving SAR operation. MF-HF SITOR (NBDP) (A) is text-based, not conducive to simultaneous voice coordination among multiple parties. Inmarsat (B) relies on routing through an RCC, creating delays and lacking direct, simultaneous multi-party communication among all participants. VHF (C) is limited to line-of-sight and short-range, failing the "long-range" requirement for communicating with distant stations or over wide SAR areas. MF-HF SSB voice is the most effective for direct, simultaneous, multi-party long-range coordination.