Letting up on the brake pedal `_________`.

A Reduces the air pressure and releases the brakes.

explanation

Letting up on the brake pedal reduces the air pressure and releases the brakes. When you press the brake pedal in a vehicle with an air brake system, it applies air pressure to engage the brakes and slow down or stop the vehicle. Releasing the brake pedal reduces the air pressure in the system, causing the brakes to disengage and release. This allows the vehicle to resume its movement.