INTERNATIONAL ONLY On open water, a power-driven vessel coming up dead astern of another vessel and altering her course to starboard so as to pass on the starboard side of the vessel ahead would sound which signal?

Correct Answer: Option D — One short blast

Rule 34(a) of the COLREGS mandates that when vessels are in sight of one another, a power-driven vessel altering course must indicate that action by the prescribed whistle signals. One short blast signifies that the vessel is altering her course to starboard, regardless of the relative position of the other vessel.