What must be checked if a vehicle has inoperative lights?

Answer: C — Electrical Wiring

When dealing with inoperative lights on a vehicle, checking the electrical wiring is crucial because it forms the foundational system that powers those lights. Faulty or damaged wiring can lead to a complete failure of the lighting system, often causing the lights to fail to operate despite being functional at the bulb level. Proper functioning of the electrical system, including wiring connections, fuses, and connectors, ensures that electricity flows to the lights as intended. Without this inspection, other potential issues may be overlooked, leading to continued problems with vehicle visibility and safety. In contrast, checking registration status, inspection approval, or signal functionality may not directly address the root cause of inoperative lights. While those elements are important in vehicle compliance and functionality, they do not provide insight into why the lights are not working, making electrical wiring the most critical aspect to inspect in this scenario.