What type of structures are equipped with a series of white lights mounted at the top?

The correct answer is related to the significance of oil well structures in marine navigation. Oil well platforms and structures are often located in open waters and can be quite tall. To enhance their visibility and safety for passing vessels, they are equipped with a series of white lights mounted at the top. These lights serve as navigational aids, helping mariners to identify the presence of these structures from a distance, especially at night or in poor visibility conditions.

While residential buildings, commercial docks, and military installations may also have specific lighting for safety or security purposes, they do not typically require the same kind of extensive lighting system as oil well structures, which are specifically designed to alert maritime traffic to their location in transit routes. The primary function of the lights on oil rigs is to prevent accidents and collisions, making them crucial components of shipping safety in maritime environments.