True or False: Braking on a long steep downgrade is just an addition to the engine's braking effect.

Answer: A — True.

Braking on a long steep downgrade is indeed an addition to the engine's braking effect. This is because while descending, engine braking alone may not be sufficient to maintain a safe speed, especially on steep grades. In such situations, the service brakes are applied in conjunction with the engine brakes to control the vehicle's speed effectively and safely. This combined approach helps to prevent overheating of the brakes and ensures that the vehicle remains stable and under control while descending. Therefore, recognizing the role of both engine and service brakes in managing speed on a downgrade is essential for safe driving practices, making the statement true.