Final answer:
The correct practice when reversing a dump vehicle to unload is to use a spotter to guide you, ensuring safety and awareness of your surroundings.
Step-by-step explanation:
When reversing to unload a dump vehicle, the safest and most professional approach is to use option c) Use a spotter to guide you. Relying solely on mirrors without checking blind spots could result in an accident, as mirrors do not cover every area behind your vehicle. Traveling at a high speed for quicker unloading is dangerous and could lead to loss of control or damage to the vehicle and the unloading area. Ignoring surrounding vehicles and pedestrians is negligent and could cause injury or damage. Therefore, the best practice when reversing to unload is to have a spotter who can guide you, ensuring that you are aware of your surroundings and able to reverse safely.