What is the primary purpose of the air brake system in a school bus?

Answer: B — To provide effective braking power using compressed air

The primary purpose of the air brake system in a school bus is to provide effective braking power using compressed air. Air brake systems are designed to utilize air pressure to operate brake mechanisms, making them highly effective for larger and heavier vehicles like school buses. This enables the vehicle to stop safely and efficiently, which is crucial for the safety of passengers and other road users. Compressed air is stored in tanks and is released to activate the brake chambers, which then engage the brake shoes or pads to slow down or stop the bus. This method of braking is preferred in heavy-duty vehicles due to its reliability and ability to handle the greater demands placed on braking systems compared to light vehicles that may use hydraulic systems. Therefore, the focus on braking power highlights the air brake system's fundamental role in protecting the safety of the bus and its occupants.