Question 459 Rules of the Road

The correct answer is D) Four short whistle blasts. The reasoning is that under the International Regulations for Preventing Collisions at Sea (COLREGS), the signal of four short whistle blasts is not one of the prescribed signals that vessels in sight of one another may use. The other three options - a light signal of at least five short and rapid flashes (A), two short whistle blasts (B), and one prolonged, one short, one prolonged and one short whistle blasts (C) - are all recognized signals under the COLREGS that vessels may use when in sight of one another. However, four short whistle blasts is not a standard signaling option in this situation.