Final answer:
The term 'Parg brake system' is not a recognized air brake subsystem. The standard subsystems include the service brake system and spring brake system, which incorporates the parking brake functionality.
Step-by-step explanation:
The question asks to identify which option is not an air brake subsystem. The correct answer is "c. Parg brake system," as "Parg" appears to be a typo or error. Typically, an air brake system for heavy-duty vehicles has several key subsystems, including:
- The service brake system, which drivers control with the brake pedal and is used for normal stops.
- The spring brake system, which is used as an emergency/parking brake.
- The parking brake system, which may also be referred to as a parking brake or emergency brake and is part of the spring brake system.
Therefore, "c. Parg brake system" does not match any known air brake subsystem and seems to be a mistaken entry.