The Rules state that a vessel overtaking another vessel is relieved of her duty to keep clear when __________.

When a vessel overtakes another vessel, the overtaking vessel is required to keep clear of the vessel being overtaken. This obligation is essential for ensuring safe navigation and preventing collisions on the water. The rule that states a vessel is relieved of her duty to keep clear when she is past and clear of the other vessel is based on the principle that once the overtaking vessel has successfully maneuvered past the other vessel and is no longer in a position to pose a risk of collision, she has fulfilled her responsibility.

At that point, the overtaking vessel can navigate freely without needing to take special measures to keep clear of the overtaken vessel. It is crucial for vessels to understand that maintaining a safe distance and ensuring that the overtaking maneuver is completed responsibly is vital in navigating safely among other vessels. The other options do not reflect the necessary conditions that would relieve the overtaking vessel from her duty. For instance, simply being directly behind, sounding a horn, or receiving a signal from the other vessel do not fulfill the requirement for an overtaking vessel to be considered past and clear.