Final answer:
The correct answer is 'All of the above' because using the lowest reverse gear when backing gives the driver more control, and stopping when the kingpin is locked ensures the trailer is securely attached.
Step-by-step explanation:
The correct answer is option C) All of the above. When backing under a trailer, it's important to use the lowest reverse gear to ensure that you have maximum control over the vehicle. This allows for fine adjustments to be made while maneuvering. Additionally, you should stop when the kingpin is locked into the fifth wheel to ensure that the trailer is securely attached to the tractor. Safely coupling a trailer is a critical skill in commercial truck driving and requires both knowledge of the equipment and attention to safety procedures.
When backing under the trailer, it is crucial to stop when the kingpin is locked into the fifth wheel. This ensures that the trailer is properly connected to the truck and prevents any accidents or damage.
Using the lowest reverse gear is not necessary when backing under the trailer. The focus should be on aligning the kingpin with the fifth wheel.