Explanation: Radio silence is a critical procedure in maritime and other emergency communications protocols, primarily dictated by international regulations like the ITU Radio Regulations. Its imposition ensures that all available listening posts can clearly receive and understand a Distress message without interference. **B) To prevent interference to Distress communications.** This is correct. A Distress call (MAYDAY) signifies that a vessel or person is in grave and imminent danger and requires immediate assistance. During a period of radio silence, all stations not involved in the distress incident are legally required to cease transmitting on the affected frequency. This creates a clear channel, maximizing the chances that the distress message is heard, understood, and acted upon promptly, which is paramount for saving lives. **A) To keep a clear channel open for Safety broadcasts.** While safety broadcasts (e.g., weather warnings, navigation hazards) are important, they do not hold the same absolute priority as a Distress message. Radio silence is not typically imposed for general safety broadcasts. **C) To allow individual vessels to carry out direct communications.** This is incorrect. Radio silence is imposed to *stop* general communications, not to facilitate them, ensuring the frequency is dedicated to the distress situation. **D) To listen periodically for other vessels sending Distress alerts on Ch-70.** While listening on Channel 70 (for Digital Selective Calling or DSC alerts) is a continuous and vital responsibility, radio silence is an active measure imposed on *transmitters* to prevent them from interfering with a voice distress call, not solely to facilitate listening.