Final answer:
The release arm is the device used to release the fifth wheel locking jaws on a tractor-trailer coupling system. It allows for the safe detachment of the trailer from the tractor by opening the locking jaws. The correct answer to the question is option C. Release arm.
Step-by-step explanation:
The question is addressing a specific component of a truck's mechanism used for coupling a trailer, specifically the release arm. The release arm plays a crucial role in the safe and secure coupling of a trailer to the tractor. When a driver needs to attach a trailer, the fifth wheel on the back of the tractor locks onto the trailer's kingpin, which is a downward-facing pin that fits into the slot of the fifth wheel. The securing of the connection between the tractor and the trailer is maintained by the locking jaws, which clasp the kingpin. When it's time to decouple the trailer, the release arm is engaged. The release arm's function is to open the locking jaws and allow the kingpin to be released. This process is essential for ensuring that trailers can be safely detached without causing any damage to the kingpin or the fifth wheel. Based on the information provided and the options listed (A. Trailer hitch B. Kingpin C. Release arm D. Tandem axle), the correct answer to the question is option C. Release arm. It is specifically designed for this purpose, contrasting with the options of the trailer hitch, which is the general connection system, the kingpin, which is part of the trailer, and the tandem axle, which refers to a set of two axles situated close together on the trailer or tractor.