Which of the following is NOT part of the equipment required on passenger cars by state law?

In Texas, state law outlines specific equipment that must be present on passenger vehicles for safety and functionality. A sunroof is not considered essential equipment required by law. While sunroofs can enhance a car's comfort and aesthetic appeal, they do not contribute to the fundamental safety features or operational requirements that are mandated for vehicles on the road.

In contrast, items like mufflers, seatbelts, and brake lights are critical for vehicle operation and safety. Mufflers help reduce noise produced by the engine, seatbelts are crucial for passenger safety by restraining occupants during sudden stops or crashes, and brake lights are essential for signaling to other drivers when a vehicle is stopping. Each of these components plays a vital role in ensuring safe driving conditions, which is why they are legally required.