Which action is recommended to ensure proper brake functionality before a trip?

Answer: B — Check air pressure and test brakes

Ensuring proper brake functionality before a trip is critical for the safety of the driver and others on the road. Checking air pressure and testing the brakes directly addresses vital aspects of the braking system. Proper air pressure in the brake system is essential since air brakes rely on compressed air to function effectively. Insufficient air pressure can lead to brake failure, which can be catastrophic. By testing the brakes, the driver can confirm that they engage and release correctly, ensuring full operational readiness. This proactive approach helps identify any potential issues, such as leaks in the air system or worn brake components, allowing for necessary maintenance before setting off on a journey. While inspecting the vehicle's exhaust system, cleaning the exterior, and verifying lights are important for overall vehicle maintenance and safety, they do not directly pertain to the functionality of the brakes. Therefore, the most critical action to focus on—especially in the context of preparing for a safe trip—remains the checking of air pressure and testing of the braking system.