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

The requirement for specific equipment on passenger cars can vary by state law, but generally, certain items are essential for safe operation and legal compliance.

Passenger cars are typically required to have functional brakes to ensure safe stopping ability, which is critical for vehicle operation and the safety of other road users. Reflectors are often necessary for visibility, especially in low-light conditions, as they help make the vehicle more noticeable to other drivers. A rearview mirror is also a standard requirement, as it aids the driver in observing traffic conditions behind them, contributing to safer maneuvering.

A loudspeaker, however, is not a standard requirement for passenger cars under state laws. While some vehicles, especially emergency vehicles or specific utility vehicles, might be equipped with a loudspeaker, it is not a common or necessary feature for ordinary passenger vehicles. Therefore, it stands out as the correct answer, as it is not typically mandated by law.