Explanation: A VHF-DSC Distress alert is always transmitted on Channel 70 (Ch-70) because it is the internationally designated and dedicated Digital Selective Calling (DSC) frequency. DSC is a digital signaling protocol used for automated maritime distress, urgency, safety, and routine calls. By having a specific, dedicated channel, all DSC-equipped radios can continuously monitor Ch-70 for these critical digital alerts, ensuring that distress signals are reliably received and acted upon. Ch-16 is the traditional voice distress, safety, and calling channel, not for digital alerts. While crucial for voice communication, DSC alerts are not sent on Ch-16. Ch-22A is a U.S. Coast Guard working channel for voice communication, often used *after* initial contact. Ch-6 is an intership safety and communication voice channel. These are all voice-oriented channels, whereas DSC requires a dedicated digital frequency for its automated signaling.