Final answer:
Part B beneficiaries are subject to coinsurance, which is a cost-sharing method where the policyholder pays a percentage of the costs while the insurance company pays the remaining amount.
Step-by-step explanation:
Part B beneficiaries are subject to coinsurance. Coinsurance is a cost-sharing method where the policyholder pays a certain percentage of the costs, while the insurance company pays the remaining amount. For example, if someone has a coinsurance rate of 20%, they would pay 20% of the costs, and the insurance company would pay 80%.