Answer: c. A-One or Best.
Step-by-step explanation:
Best Collection Company are the ones who cause the accident and so they can be held liable and have to compensate Carl for injuries and harm caused.
Best however, was acting as an agent on behalf of A-One Auto Sales so A-One can be held liable as well for the incident. Carl can therefore also be compensated by A-One as well.
Carl cannot be compensated by both for the same incident as this amounts to double compensation but can be compensated by either one of them.