What is the primary purpose of a Marketplace plan’s formulary?

The primary purpose of a Marketplace plan’s formulary is to detail the medications covered by the health plan. A formulary is essentially a list that provides information on which prescription drugs are included in a health insurance policy. This list is crucial for members because it helps them understand what medications will be covered under their plan, including any potential restrictions, such as prior authorizations or tiered pricing structures. Understanding the formulary can significantly affect a member's healthcare choices, as it directly relates to the affordability and accessibility of necessary medications. Thus, option C accurately reflects the intended function of a formulary within a health insurance context.