Final answer:
The question is about the distance a tractor should be pulled forward after unhooking from a trailer for safety reasons. The correct distance varies by safety practices, but generally, it should be sufficient to ensure the trailer won't reconnect accidentally and to allow a safety inspection.
Step-by-step explanation:
The question pertains to the procedure after unhooking a tractor from the trailer, specifically regarding the safe distance the tractor should be pulled forward. It is important to understand the context and safety practices in truck operation to answer this question. Typically, after unhooking a trailer, a standard safety practice is to pull the tractor forward enough so the trailer will not be accidentally reconnected if the tractor is moved back, and to ensure all connections like airlines and electrical lines have enough clearance. While I cannot provide a direct answer from the choices given without more context, as different companies and scenarios might require different distances, it's common to pull forward at least far enough to perform a safety inspection around the trailer. For passing a practical test or according to specific safety guidelines, the required distance may be specified in a driver's manual or by the testing authority.