What major guideline does Rule 31 present?

Answer: B — Rules on maintaining a safe distance in navigational traffic

Maintaining a safe distance in navigational traffic is the main idea here. Rule 31 emphasizes keeping enough space between your vessel and others so that there’s time to react and avoid collisions under the current conditions. This means you plan your speed and course with the surrounding traffic in mind, considering factors like vessel size and maneuverability, weather, visibility, currents, and how busy the area is. The goal is to act early and decisively—slowing down, changing course, or choosing a safer passing distance—so that a safe separation is always maintained. Other options address topics outside this collision-avoidance focus, such as vessel inspections, construction materials, or emergency signaling, which are covered by different rules or regulations.