What actions are required by ships operating in a narrow channel according to Rule 9?

The correct answer reflects the essential principles outlined in Rule 9 of the COLREGs, which governs vessels navigating in narrow channels. This rule specifies that vessels must keep to the starboard side of the channel whenever possible and emphasizes the need to avoid anchoring within the channel itself. This is crucial for ensuring safe and efficient navigation, as narrow channels often accommodate multiple vessels, and adhering to the starboard-side rule helps maintain predictable traffic patterns.

By avoiding anchoring within the channel, ships minimize the risk of collisions and allow for the smooth passage of both upstream and downstream traffic. This is particularly important because the limited width of a narrow channel means that there are fewer options for vessels to maneuver safely. Thus, maintaining one side of the channel for navigation keeps the pathway clear for all vessels.

In contrast, other choices do not align with the regulations specified in Rule 9. Allowing vessels to anchor anywhere in the channel poses considerable risks to navigation, while operating at maximum speed contradicts the need for caution in confined waterways. Lastly, navigating with reduced sail area is not a requirement in Rule 9, though vessels should always adjust sail area and speed based on conditions for safe operation. The emphasis is on traffic management and prevention of collisions in the constrained environment