Final answer:
The increasing number of parties involved in the Coase theorem scenario suggests a difficulty in reaching a private solution as bargaining costs increase.
Step-by-step explanation:
The increasing number of parties involved in the Coase theorem scenario suggests that there is a difficulty in reaching a private solution (c) as bargaining costs increase. When there are more parties involved, the complexity of the negotiation process increases. The costs associated with coordinating and reaching an agreement among multiple parties can become prohibitive, making it more challenging to find a mutually acceptable solution.