How does an air brake system operate in a truck?

An air brake system in a truck operates by utilizing compressed air to generate the force needed to apply the brakes, making option B the correct choice. In this system, air is compressed and stored in tanks, which is then released when the driver applies the brakes. This release of compressed air activates components such as brake chambers, which push the brake shoes against the drums or rotors to slow down or stop the vehicle.

The use of compressed air in braking systems is advantageous for larger vehicles, as it provides consistent and strong braking power that can handle the heavy loads often carried by trucks. The air brake system is designed to work effectively in various conditions, making it a preferred choice in commercial truck applications.

The other options do not accurately describe how an air brake system operates. While hydraulic systems are common in light vehicles, they do not apply to air brakes in trucks. Similarly, electric signal braking systems are used in some modern applications but are not the standard for heavy trucks' air brake systems. Mechanical levers can be part of the braking mechanism but are typically engaged through the air pressure rather than being the primary means of activation. Thus, option B accurately reflects the air brake operation essential for safety and performance in trucking.