According to Rule 19d, what should a vessel avoid if altering course?

In the context of Rule 19d of the COLREGs, the correct consideration focuses on navigation safety and the behavior of vessels in close quarters. When a vessel is maneuvering, particularly regarding its course, it must be vigilant about the potential risk of collision. Specifically, altering course to port when the other vessel is ahead of the beam can increase the likelihood of a collision, as it reduces the distance between the two vessels.

The rule emphasizes the need for vessels to maintain a safe distance and makes it clear that certain maneuvers, such as turning to port in this scenario, may not be prudent as it can place both vessels on a collision course. This is especially critical when two vessels are nearing each other, necessitating that they analyze the risks of their movements carefully and take actions that will maximize safety on navigational waters.

In comparison, the other options do not align as precisely with the intent of Rule 19d regarding the specific actions a vessel should take to avoid hazardous situations associated with changing course. For example, altering course to starboard does not carry the same immediate risk of collision when overtaking. Changing speed can be a strategic maneuver, while navigating close to maritime boundaries is more related to jurisdictional issues rather than immediate vessel interaction