Under the Rules, what should a vessel accomplish by slacking her speed, stopping, or reversing her engines?

The correct choice reflects the importance of safety and situational awareness in navigation. When a vessel slacks her speed, stops, or reverses her engines, it allows the crew aboard to better assess the surrounding conditions and potential hazards, such as other vessels, navigational aids, or environmental factors. This deliberate action is critical in preventing close-quarter situations where quick judgment is necessary. By taking these measures, the crew can gain a clearer perspective of the situation, ensuring that they can make informed decisions about navigation, maneuverability, and safety protocols.

The other alternatives do not align with the primary objective of reducing speed or stopping a vessel. While reducing fuel consumption can be a secondary benefit of these actions, it is not the main focus under the Rules of the Road. Preparing for docking is also a valid operational maneuver but does not encompass all scenarios covered by the Rules when a vessel needs to evaluate its environment. Lastly, signaling other vessels to keep clear is important but is not necessarily achieved by slowing down or stopping. The main takeaway is that reducing speed, stopping, or reversing are crucial practices meant to enhance safety and situational assessment on the water.