Final answer:
The best way to use brakes when going down hills is to downshift before the descent, which is known as engine braking. This practice avoids overheating the brakes and ensures better control of vehicle speed.
Step-by-step explanation:
The recommended practice for using brakes when going through hills is to downshift before the descent (option c). This technique, known as engine braking, helps control speed effectively without overheating the brakes. The problem with using brakes continuously is that truck brakes convert gravitational potential energy into increased internal energy, which can raise the temperature of the brake material significantly. This is due to the large mass of the truck in comparison to the brake material, making heat transfer to the environment inefficient. In contrast, regenerative braking in hybrid and electric vehicles converts this mechanical energy into electrical energy stored in the battery.
It's important to avoid continuous use of the brakes as this might lead to brake failure from overheating. Before descending a hill, it's best to downshift to use engine braking to help control the vehicle's speed. This method reduces the reliance on the brake material, preventing excessive heat build-up and potential brake fade or failure.