Question 600 Rules of the Road

The correct answer is D) When any vessel fails to understand the intentions of an approaching vessel she must sound the danger signal. The danger signal is defined in both the International and Inland Navigation Rules as 5 or more short and rapid blasts of the whistle, which indicates uncertainty about the other vessel's intentions or actions. According to the rules, this signal must be sounded when a vessel is in doubt about the intention or action of another vessel, in order to alert the other vessel and draw attention to a potentially dangerous situation. The other answer choices are incorrect - the danger signal is not limited to only the stand-on vessel, it consists of 5 or more short blasts, and distress signals are separate from the danger signal.