How often must the brake lights of your vehicle be functioning properly?

Answer: B — At all times when the vehicle is in operation

The correct answer emphasizes that the brake lights of your vehicle must be functioning properly at all times when the vehicle is in operation. This is crucial for safety on the road, as brake lights signal to drivers behind you when you are slowing down or coming to a stop. Properly functioning brake lights help prevent rear-end collisions and ensure that other drivers can react appropriately to your braking actions. Regardless of the time of day, weather conditions, or specific driving environments like highways versus local streets, keeping brake lights operational is a fundamental requirement for safe driving. This requirement applies universally, ensuring that all vehicles on the road communicate their stopping intentions effectively to all other road users.