Question 857 Rules of the Road

The correct answer is D) Two green lights. According to the International and Inland Navigation Rules, a dredge or other obstruction to navigation at night is required to display two green lights to indicate the side on which another vessel may pass. This signals to other vessels the location of the obstruction and the safe side for passing. The other options are incorrect because red lights are typically used to indicate the port (left) side of a vessel, while a single white light would not provide the necessary information about the obstruction. Two green lights specifically communicate the safe passage route around the dredge or obstruction.