Final answer:
The coverage extension that would cover the damage to the trailer is Non-Owned Detached Trailers.
Step-by-step explanation:
The coverage extension that would cover the damage to the trailer is Non-Owned Detached Trailers. Non-Owned Detached Trailers coverage provides insurance for trailers that are not owned by the insured, but are in their care, custody, and control. In this case, the trailer belongs to the respective buyers, but Jim's business is responsible for loading it.