What is the primary rule regarding lights displayed by a power-driven vessel underway at night?

A power-driven vessel underway at night is required to display specific lights to ensure safe navigation and to signify its presence to other vessels.

The requirement for lights is detailed in the International Regulations for Preventing Collisions at Sea (COLREGs). A power-driven vessel must show a white masthead light, which is visible from a distance of at least one mile. Additionally, it must display sidelights (red on the port side and green on the starboard side) and a stern light. These lights serve important safety functions: the masthead light indicates the vessel's position and heading, the sidelights help other vessels determine the direction the power-driven vessel is moving, and the stern light assists in identifying the vessel's size from the rear.

Therefore, all of these lighting requirements are crucial for night navigation and collision avoidance, which is why the comprehensive option encompasses all these necessities.