What type of vessels must monitor VHF Channel 70?

VHF Channel 70 is designated as the distress and calling frequency for the Global Maritime Distress and Safety System (GMDSS). All vessels equipped with GMDSS must monitor this channel to ensure they can promptly receive and respond to distress calls and safety messages. The GMDSS is a vital communication system designed to enhance safety at sea, and monitoring Channel 70 is a key component of that system.

This requirement applies universally to all vessels equipped with GMDSS, which includes a wide range of ships such as passenger vessels, cargo ships, and fishing boats, beyond just the specific types of vessels listed in the other choices. Therefore, the choice specifying that only commercial fishing vessels, only leisure craft, or only cargo vessels over a certain size are required to monitor Channel 70 is not accurate since it omits other types of vessels that also must adhere to these safety protocols.