Explanation: Upon hearing an SOS, which signals a grave and imminent danger, all radio stations are legally obligated to give absolute priority to the distress traffic. Immediately ceasing all transmissions (B) ensures that the distress signal can be clearly heard by all relevant parties, including rescue authorities, and that subsequent vital communications related to the emergency are unobstructed. This fundamental regulatory requirement prevents any accidental interference with critical distress calls and the coordinated response. Repeating the SOS to all traffic (A) is generally unhelpful and can actually exacerbate the situation by needlessly cluttering the frequency, potentially interfering with the original distress call or the response of rescue services. Similarly, contacting the vessel in distress (C) should only be done if you are able to render immediate, direct assistance or are specifically called upon. Otherwise, such a transmission would also add to congestion, hindering effective communication. The primary action for most operators is to maintain radio silence on the frequency to keep it clear.