What component is primarily responsible for adjusting the brakes in an air brake system?

Answer: B — Brake adjuster

The component that is primarily responsible for adjusting the brakes in an air brake system is the brake adjuster. This apparatus ensures that the brake shoes maintain the proper distance from the brake drum. By automatically or manually adjusting as the brake shoes wear down, the brake adjuster helps ensure that the brakes function effectively and safely. Maintaining the correct spacing between the brake shoes and drum is critical for optimal braking performance. If the adjustment is not made, the distance can increase, resulting in reduced braking efficiency and longer stopping distances. Thus, the role of the brake adjuster is fundamental for the overall safety of the vehicle. In contrast, while other components like the brake actuator and pneumatic control valve play crucial roles in the air brake system—such as applying the brakes and controlling the flow of air—they do not specifically handle the adjustment of the brakes themselves. The power steering pump has no relation to the braking system, as it is designed to assist with steering, not braking adjustments.