What components make up the basic air brake system?

The correct choice identifies the fundamental components that are essential for the operation of an air brake system. The brake pipe is a crucial part of the system, as it carries compressed air from the locomotive to the cars, enabling the brakes to engage. The air reservoir serves as a storage tank for the compressed air, ensuring that there is always a supply available for braking purposes. The brake cylinders are the mechanical devices that convert the air pressure into force, which then applies the brakes to the wheels of the train.

In contrast, the other options contain components that do not directly pertain to the air brake system. While brake levers, air valves, and pressure gauges can play supporting roles in various braking systems or operations, they do not represent the fundamental components of an air brake system. Components such as train wheels, couplers, and safety chains are primarily related to the structural integrity and mechanical coupling of train cars, rather than the braking mechanism. Similarly, control panels, signal lights, and track switches are associated with train operation and management but are not part of the air brake system itself.