Which vessel is required to alter course when two boats meet head-on?

When two vessels are approaching each other head-on, the general rule of navigation is that both vessels should take action to avoid a collision. However, the responsibility for altering course primarily falls to the vessel that is under power. This is because powered vessels are better equipped to maneuver quickly compared to sailing vessels that rely on wind direction and strength for their movement.

In typical conditions, the powered vessel should give way to the sailing vessel, which must maintain its course. This distinction is critical for ensuring safety on the water, as it promotes predictable behavior between different types of vessels. The powered vessel usually has the ability to change speed or direction more easily, which is why it assumes the responsibility to navigate away from the potential path of collision.

The other choices refer to different circumstances or vessels that do not specifically apply to the situation described. For example, the sailing vessel's direction from the port or the starboard is relevant to other rules of navigation but does not dictate the requirement to alter course in a head-on meeting situation like the powered vessel does.