What should a vessel operating in fog do according to the Rules?

Answer: B — Proceed at a safe speed and sound the appropriate fog signals

A vessel operating in fog should proceed at a safe speed and sound the appropriate fog signals to ensure safety and compliance with navigation rules. Operating at a safe speed is crucial because it allows the vessel to maneuver effectively should it be necessary to take evasive action in response to other vessels or obstacles that may be difficult to see in reduced visibility conditions. Sounding the appropriate fog signals is equally important, as it helps to alert other vessels of your presence in the area, reducing the risk of collision. The specific sounds, like prolonged blasts on the horn, are well-defined in the navigation regulations and serve as crucial communication tools during incidences of low visibility. In contrast, increasing speed may lead to a higher risk of collision since it decreases the vessel's ability to react to unseen obstacles or other vessels. Anchoring can be a reasonable action depending on the circumstances, but it doesn't ensure continued awareness of nearby traffic. Turning off navigation lights would be dangerous and is against the rules, as it would prevent other vessels from seeing your vessel’s position.