Practice question

What is the primary cause of a 'runaway' heavy truck on a long mountain descent?

Descending in too high a gear while continuously riding the service brakes, resulting in thermal brake fade and total loss of friction
Overfilling the engine radiator with coolant
Driving with the air conditioning turned on
Having full fuel tanks

Answer: A — Descending in too high a gear while continuously riding the service brakes, resulting in thermal brake fade and total loss of friction

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