What is the meaning of "air brakes" in commercial driving?

The term "air brakes" in commercial driving refers specifically to a braking system that functions by using compressed air to operate the brakes. This system is prevalent in large vehicles, including trucks and buses, due to its effectiveness in generating the force needed to engage the brakes on heavier loads. Air brakes utilize air pressure to push a piston that activates the braking mechanism, providing reliable stopping power, especially important for larger vehicles that require greater braking force.

This technology allows for a more robust and consistent braking experience, particularly in situations where a vehicle is subject to frequent stops or has substantial weight. Air brake systems also include safety features such as a spring brake that engages automatically if air pressure drops, ensuring that the vehicle can be stopped safely even if there is a failure in the air system. This context makes "C" the correct answer, as it accurately captures the essential operation and principle behind air brakes in commercial driving scenarios.