Final answer:
Medicare Part D plans have flexibility in managing how enrollees access medications; they do not have to cover all medications and can use tiered co-payments and prior authorization among other cost containment strategies.
Step-by-step explanation:
The correct answer to the question about the types of tools that Medicare Part D prescription drug plans can use to affect how enrollees access medications is: c. Part D plans do not have to cover all medications. As a result, their formularies, or lists of covered drugs, will vary from plan to plan. In addition, they can use cost containment techniques such as tiered co-payments and prior authorization.
It's important to understand that while Medicare Part D has significantly improved access to prescription drugs for the elderly and disabled, the plans vary and may employ different strategies to manage costs. This includes not covering certain drugs, utilizing a formulary that lists which medications are covered, and implementing cost-sharing methods to influence drug choices and usage.