When power-driven vessels "A" and "B" are meeting on a river, what action should they take?

Answer: C — Exchange two blast whistle signals and pass starboard to starboard

When two power-driven vessels are meeting head-on, the preferred action according to the navigation rules is for both vessels to pass starboard to starboard. This ensures that both vessels maintain a safe distance from each other while navigating in the limited space of a waterway. Exchanging two blast whistle signals indicates that both vessels agree to this maneuver, reinforcing the intention to pass right side to right side, which is the standard practice in maritime navigation. By adopting this approach, both vessels avoid any potential for collision and ensure a clear and predictable passage for each. In contrast, the idea of merging into the center of the river may create confusion and increase the risk of collision if both vessels attempt to do so at the same time. Similarly, stopping and anchoring could lead to obstructing navigation for other vessels. Lastly, while exchanging one blast signals might seem like a courteous gesture, it does not align with the established protocol for meeting vessels, which specifically calls for clarity and safety by passing starboard to starboard.