What is the role of the brake pedal in an air brake system?

Answer: C — To regulate air supply to brake chambers

In an air brake system, the role of the brake pedal is to regulate air supply to the brake chambers. When the brake pedal is pressed, it activates the master cylinder, which then reduces the air pressure in the brake system, allowing the stored compressed air to flow into the brake chambers. This air pressure is what engages the brake actuators, causing the brake shoes to press against the brake drums and slow down or stop the vehicle effectively. Understanding the function of the brake pedal is crucial for safe operation, as it is the primary means by which a driver controls the braking force applied to the vehicle. In this context, other options do not pertain to the specific function of the brake pedal within the air brake system. For example, increasing engine power pertains to engine throttle control, engaging the parking brake is typically done through a separate mechanism from the main brake pedal, and monitoring tire pressure involves tire management rather than braking operation.