Question 816 Rules of the Road

The correct answer is A) when her sidelights and stern light are combined in one lantern and shown on the mast. The reason this is the correct answer is that under both the International and Inland Navigation Rules, a sailing vessel is not allowed to display the all-round red over green lights on the mast if her sidelights and stern light are combined in one lantern and shown on the mast. This is because the all-round red over green lights are used to indicate a sailing vessel under power, not a sailing vessel under sail. The other options are incorrect because they do not address the specific condition of the sidelights and stern light being combined in one lantern on the mast, which is the key factor that determines when a sailing vessel cannot display the all-round red over green lights.