What should a driver do if the low air warning signal activates while driving?

Answer: A — Gradually stop the vehicle and check the air brake system

When the low air warning signal activates while driving, the appropriate action is to gradually stop the vehicle and check the air brake system. This is crucial because the low air warning indicates that the air pressure in the brake system has dropped below a safe level, which can significantly impair braking performance. By stopping the vehicle safely and promptly, the driver ensures they can assess the situation without endangering themselves or others on the road. Addressing the warning immediately helps prevent potential brake failure, which can lead to serious accidents. Once stopped, the driver can inspect the air brake system for leaks, confirm if the pressure is within operational limits, and determine the necessary actions to take, whether it's making repairs or contacting assistance. In this context, the other choices do not prioritize safety and risk further complications. Increasing speed or continuing to drive disregards the warning and can lead to dangerous situations. Ignoring the warning signal is not wise, as it compromises the safety and functionality of the vehicle.