Which type of distress signal requires immediate confirmation of receipt?

The option indicating that distress alerts sent via radio or Digital Selective Calling (DSC) require immediate confirmation of receipt is accurate because these signals are designed for urgent communication and safety in maritime operations. When a ship sends a distress alert via radio or DSC, the expectation is for other vessels or shore stations to promptly acknowledge the receipt of this critical information. This immediate acknowledgment ensures that rescue operations can be efficiently coordinated, and the distressed vessel receives the necessary assistance as quickly as possible.

In contrast, visual flag signals, sound signals, and flares and smoke signals do not have the same immediate confirmation requirement built into their protocols. While these signals are also used to indicate distress, they rely on visual or auditory observation, which can be subject to delays in acknowledgment, and there is no formal acknowledgment process like with radio and DSC distress alerts. This fundamental difference highlights why distress alerts sent through radio and DSC are prioritized for immediate confirmation in maritime safety communications.