What is the key advantage of using lower gears on steep descents?

Using lower gears on steep descents is advantageous primarily because it prevents overheating of the brakes. When descending a hill, a vehicle can gain considerable speed due to gravity. If a driver relies solely on brakes to control this speed, the brakes can overheat from the continuous friction, potentially leading to brake fade, where the brakes become less effective. By shifting to a lower gear, the engine can assist in controlling the vehicle's speed through engine braking. This reduces the reliance on the brakes and helps maintain their optimal temperature, ensuring they remain effective throughout the descent.

The other options present benefits that are not the primary focus of using lower gears. While enhancing driver control is an important aspect, the most critical aspect in the context of managing steep descents is the prevention of brake overheating.