What does a vessel greater than 100 meters need to display when anchored?

Answer: A — All deck lights on

A vessel greater than 100 meters in length needs to display specific lights when anchored to ensure visibility and safety during the night or in poor visibility conditions. The correct requirement is to display all deck lights on. This practice enhances the visibility of the vessel and helps other vessels in the vicinity identify its location and size, which is particularly important in busy waterways or at night. Displaying all deck lights serves multiple purposes: it provides an illuminated outline of the vessel, helps prevent collisions by making the vessel more conspicuous, and enables other mariners to assess its presence accurately. The other options listed do not meet the comprehensive lighting requirements established by the COLREGs for vessels of this size. For instance, showing only one all-around light or a stern light would not sufficiently ensure that the vessel is visible to other mariners, as it does not provide enough illumination to convey the overall dimensions and location of the anchored vessel to observers approaching from different angles.