Final answer:
Option B. The system that connects the tractor and trailer is the coupling system, which often includes the kingpin as part of its locking mechanism.
Step-by-step explanation:
The system that connects the tractor and trailer is known as the coupling system. This is a critical component in heavy machinery and vehicles, particularly in the trucking industry where a tractor must be securely attached to a trailer. The coupling system often involves a kingpin, which is a part of the mechanism that the trailer provides to lock it into place with the tractor.
The system that connects the tractor and trailer is called the Coupling system. It is responsible for securing the connection between the two components and ensuring their coordinated movement. The coupling system typically consists of a coupling device, such as a fifth wheel or a kingpin, which allows the tractor and trailer to pivot and rotate together.
The kingpin system can be seen as a component or a type of coupling system, but the correct answer to the question is 'B. Coupling system' because it is the broader term that encompasses the entire mechanism used to connect a tractor with a trailer.