Explanation: Under the Global Maritime Distress and Safety System (GMDSS), survival craft radiotelephony equipment is designed for crucial communication during distress. Channel 16 (Ch-16), operating at 156.8 MHz, is the internationally recognized maritime VHF voice distress, safety, and calling frequency. Equipping survival craft with Ch-16 capability ensures that those in distress can make direct voice contact with rescue vessels, aircraft, or shore stations monitoring this vital channel. Option A (457.525 MHz) is a common frequency for on-board communications, not for external distress calls. Option C (121.5 MHz) was an older aviation emergency frequency, now largely superseded and not used for GMDSS survival craft voice. Option D (Ch-70) is the dedicated international DSC (Digital Selective Calling) distress and safety frequency for automated digital alerts, not for voice radiotelephony.