Explanation: The Global Maritime Distress and Safety System (GMDSS) fundamentally aims to ensure maritime safety through improved communications. Answer C accurately reflects this core responsibility: every ship operating under GMDSS is equipped and able to perform essential communication functions for its own safety and to facilitate the safety of other ships in distress. This includes transmitting and receiving distress alerts, maritime safety information, and general communications. Answers A, B, and D are incorrect because they confuse GMDSS's communication mandate with the general international obligation to render assistance. While GMDSS *facilitates* the coordination of assistance by enabling reliable communication, its direct responsibility is not to define *who* renders assistance, or under what specific conditions (like vessel size, proximity, or impact on port schedule). The duty to render assistance is a separate, broad international maritime law requirement that applies to all vessels, independent of their GMDSS sea area classification (A1, A2, A3, A4).