Explanation: The Reserve Source of Energy (RSE) in GMDSS is a critical safety feature, designed to ensure distress communication capability even if a vessel loses its main power supply. The correct answer, C), highlights this crucial independence. When the ship's primary electrical system fails, the RSE (typically batteries) must be able to autonomously power the GMDSS equipment. This requires it to be entirely independent of the main electrical system to perform its function effectively during an emergency. A) is incorrect because the RSE is a *source* of power, not about supplying *independent installations*. B) is incorrect. The RSE *must* be independent of the ship's propelling power (which generates main electricity) to ensure operation during a main power failure. D) is misleading. While it's connected for charging, its emergency function demands independence from the main system when supplying power.