Question 899 Rules of the Road

The correct answer is D) There is doubt that another vessel is taking sufficient action. Five or more short blasts on a vessel's whistle indicate uncertainty or doubt that the other vessel is taking sufficient action to avoid a collision, as per the International Regulations for Preventing Collisions at Sea (COLREGS). This is a warning signal to alert the other vessel that immediate action may be required to avoid a collision. The other answer choices are incorrect because they do not accurately reflect the meaning of the five or more short blasts signal, which is to indicate doubt about the other vessel's actions, not to indicate a change in course or speed.