What type of lights must a 15-meter sailing vessel display?

A 15-meter sailing vessel is required to display sidelights and a stern light, which can be combined into a single lantern on the mast. This requirement helps to ensure that the vessel is visible to other boats, particularly at night or in low-visibility conditions. The sidelights are positioned to indicate the port and starboard sides, while the stern light is located to show the rear of the vessel. Using a combined lantern simplifies the lighting setup while still adhering to safety regulations, making the vessel easier to spot without overcrowding the equipment necessary for safe navigation.

Other options might suggest the need for additional or separate lights that are not strictly required for a 15-meter sailing vessel under the regulations. The simplicity of having a combined lantern reflects practical and safety considerations for vessels of this size.