What testing practice is essential to maintain air brake efficiency during normal operations?

Answer: B — Conducting routine brake system checks and maintaining records

Maintaining air brake efficiency during normal operations is primarily achieved through conducting routine brake system checks and maintaining records. Regular inspections of the brake system are essential to identify any issues that could impair braking performance, such as leaks, worn-out components, or deficiencies in air pressure. By keeping thorough records of these inspections and any maintenance performed, operators can track the condition of the braking system over time and ensure that all necessary adjustments or repairs are made promptly. This proactive approach helps to prevent brake failures, enhances safety for both the crew and passengers, and is a critical best practice in the operation of trains. While the other choices focus on different operational aspects, they do not directly contribute to the specific maintenance and efficiency of the air brake system, which is crucial for safe train operations.