What must a vessel do when navigating in restricted visibility?

When navigating in restricted visibility, a vessel is required to sound appropriate signals. This is essential for communicating its presence to other vessels nearby, as visibility may be significantly impaired due to fog, rain, or other conditions. The sound signals help other vessels determine where you are and what your intentions might be, allowing for safer navigation and avoidance of collisions.

While the other options may seem relevant, they do not align with the specific requirements for vessels in restricted visibility. For instance, maintaining current speed without alteration could lead to dangerous situations if the vessel cannot see obstacles or other ships. The use of radar is beneficial but is not mandatory at all times in these conditions, as not all vessels are equipped with radar. Similarly, following the path of least resistance does not consider the safety measures and prudent navigation practices that must be undertaken in low-visibility scenarios. Thus, sounding appropriate signals is the key action mandated under the Rules of the Road.