What lights should a sailing vessel display at night?

A sailing vessel must display specific lights at night to ensure visibility and indicate its status. The correct answer states that a sailing vessel should exhibit red and green sidelights along with one all-round white light.

The red and green sidelights serve to indicate the direction the vessel is facing and its relative position to other vessels. The red light is displayed on the port side (left when facing forward), while the green light is on the starboard side (right when facing forward). These sidelights alert other vessels to the sailing vessel's orientation and movement.

The addition of the all-round white light is crucial as it indicates that the vessel is under sail, distinguishing it from other types of vessels, such as power-driven ones. This all-round white light is typically displayed at the top of the mast or in a position that offers maximum visibility to other mariners.

In contrast, the other choices do not provide the appropriate combination of lights required for a sailing vessel, leading to potential confusion on the water regarding its navigation status. Therefore, the combination of red and green sidelights along with one all-round white light is essential for compliance with maritime navigation rules.