What lighting equipment must all trailers or semi-trailers have if their width is 80 inches or more?

Trailers or semi-trailers with a width of 80 inches or more are required to have specific lighting equipment to ensure visibility and safety on the road. The correct response identifies that these vehicles must be equipped with clearance lamps, side marker lamps, and side reflectors.

Clearance lamps are mounted on the front and rear of the vehicle to indicate its overall width, while side marker lamps help increase visibility from the side, particularly during low-light conditions. Side reflectors serve a similar purpose, enhancing the vehicle's visibility by reflecting light from other vehicles, making it easier for approaching drivers to gauge the width and presence of the trailer. Together, these components contribute to safer navigation by minimizing the risk of accidents due to insufficient visibility for larger vehicles on the road.

Other options mentioned do not fulfill the regulatory requirements for trailers of this width, making the correct answer essential for compliance with safety standards.