Final answer:
The salesperson must hold the offer until the listing company can be contacted.
Step-by-step explanation:
The correct answer is c. Hold the offer until the listing company can be contacted. In this situation, the salesperson should wait until they are able to reach someone at the listing office to present the offer. This is the ethical and professional approach to handling the situation, as the salesperson should have the opportunity to present the offer to the appropriate party. If the salesperson returns the offer to the potential buyer without making any effort to contact the listing office, it could potentially harm their professional reputation.