Explanation: Upon receiving a DSC Distress alert, the primary immediate actions for a vessel are to inform the Master and switch to monitor VHF Channel 16. DSC is a signaling system designed to alert other stations to an urgent situation and indicate which voice channel to switch to for further communication. For distress, this is universally Channel 16. Monitoring Ch-16 allows you to hear the distressed vessel's subsequent voice MAYDAY call and assess the situation or render assistance if able. Advising the Master ensures the person in command is aware and can make informed decisions. Transmitting a DSC acknowledgment (A) is generally reserved for Coast Stations or designated Rescue Coordination Centers, as ship-to-ship DSC acknowledgments can cause confusion or block the distress frequency. While calling the Coast Guard (B) may be necessary later, your immediate action as a vessel should be to monitor the voice channel. No action (C) is irresponsible and unsafe.