What are the two main types of air brakes?

The correct answer identifies the two primary types of air brakes as service brakes and parking brakes. Service brakes are used during regular operation to slow down or stop the vehicle, allowing a driver to control speed and ensure safe stopping during travel. These brakes are typically activated by pressing the brake pedal and operate using compressed air to apply brake force to the wheels.

Parking brakes, on the other hand, are designed to secure the vehicle when it is parked, preventing it from rolling away. They can be engaged manually and remain effective even when the vehicle's main system is not in operation. This dual system is essential for safety, as it ensures that vehicles remain stationary when parked and can be effectively controlled during operation.

The other choices, while they mention brake systems, do not distinguish between the two main types of air brakes as clearly. Air brakes and hydraulic brakes refer more to the operational principles rather than the specific categories of brakes in an air brake system. Standard brakes and anti-lock brakes also do not reflect the primary classifications found in air brake systems, focusing instead on specific features rather than overall types.