What regular action can be performed to maintain the integrity of the air brake system?

Answer: C — Inspect air lines for wear and tear

Regularly inspecting air lines for wear and tear is vital for maintaining the integrity of the air brake system. Air lines are crucial components that transport compressed air from the compressor to the brake chambers. Any damage, such as cracks, abrasions, or deterioration, can lead to air leaks, which undermine the system's effectiveness and potentially compromise safety by reducing braking power. This inspection helps to ensure that the air brake system operates efficiently and reliably, preventing failures that could occur due to wear or environmental exposure. The other options, while they contribute to overall vehicle maintenance, do not directly pertain to the air brake system's integrity. Tire pressures affect traction and handling, brake fluid levels pertain to hydraulic brake systems rather than air brakes, and engine oil replacement is associated with engine performance rather than braking systems. Hence, these actions, although important for vehicle maintenance, do not specifically address the air brake systems' condition in the same way that inspecting air lines does.