When is it preferable for a vessel to alter course instead of speed?

Answer: B — When it makes the change more obvious to other vessels

Altering course is preferable when it makes the change more obvious to other vessels. This is essential for maintaining navigational safety, as clearly demonstrating a change in course helps prevent misunderstandings between vessels. When one vessel alters its course, it signals its intention more clearly than merely adjusting speed, which may be less visible to other operators. A visible maneuver, such as a noticeable course change, can significantly reduce the risk of collision, especially in crowded or complex navigation situations. In situations where visibility is poor, moving at high speed, or with larger vessels, simply changing speed may not be sufficient to effectively communicate intentions to other vessels. In such cases, altering course becomes a more effective way to ensure that nearby vessels accurately perceive the vessel's actions and intentions.