Final answer:
Before backing a large truck, the first step is to get out and carefully check the clearance limits to ensure that there are no hazards or obstructions behind the vehicle.
Step-by-step explanation:
The first step you should take before backing a large truck is to get out and carefully check clearance limits. This action is crucial to ensure there are no obstructions or hazards behind the vehicle that could cause an accident during the backing maneuver. Safety is of utmost importance when operating large vehicles like trucks, and external checks are part of standard safety protocols.
Regarding the factors like the distance the driver covers before hitting the brakes, how long it takes the truck to stop after hitting the brakes, and the total distance the truck covers to stop, this information is essential for understanding stopping distances, vehicle dynamics, and safety margins, but it is not directly related to the initial step of backing up a truck, which is ensuring a clear path.
This is done to ensure that there is enough space for the truck to maneuver without hitting any obstacles or structures. By checking clearance limits, the driver can avoid potential accidents or damage to the truck.
Therefore the correct answer is a. get out and carefully check clearance limits.