What is necessary to signal a power vessel that is making way?

In the context of navigational rules under the COLREGs, a power vessel that is making way does not require a sound signal. When a vessel is underway and making way, that indicates it is actively moving through the water, and due to the nature of its operation, it is not mandated to signal its presence or activity through sound signals unless it is approaching a specific situation, such as another vessel or a restricted area where a signal may be prudent for safety.

Sound signals are typically reserved for particular situations or maneuvers, such as when vessels are in sight of one another and are uncertain of each other’s intentions. The absence of sound signal requirements for a power vessel making way reflects the understanding that its operational status is already clear.

Given this status, the other choices involve various sound signaling methods that would be used for either vessels at anchor, vessels not making way, or specific signaling situations, none of which apply to a power vessel that is already in motion. Therefore, the correct understanding aligns with choice A, which indicates that no sound signal is necessary for a power vessel that is making way.