What is the function of the low-air warning system?

Answer: B — To alert the driver when air pressure drops below safe levels

The function of the low-air warning system is to alert the driver when air pressure drops below safe levels. This is critical because air brakes rely on compressed air to function properly. When the air pressure falls below a specified threshold, it can compromise the effectiveness of the braking system, potentially leading to unsafe driving conditions. The low-air warning system serves as an essential safety feature, ensuring that the driver is immediately informed of any drop in air pressure, allowing them to take appropriate action before a failure occurs. This proactive notification helps prevent accidents and maintains vehicle control. The other options do not address the primary purpose of the system. For instance, notifying passengers of a malfunction does not focus on the critical function of ensuring the brakes are operational. Engaging the brakes automatically is a different mechanism and is not related to the warning system, while engine temperature indicators pertain to the engine's performance and safety rather than the braking system's air pressure.