Final answer:
Medicare Part D coverage includes a coverage gap known as the "donut hole" where the insured pays a higher percentage of the cost of prescription drugs.
Step-by-step explanation:
The correct answer is 4) Donut hole.
Medicare Part D coverage includes prescription drug benefits. However, there is a coverage gap known as the "donut hole." When an insured reaches their initial benefit limit, they enter the donut hole phase where they must pay a higher percentage of the cost of their prescription drugs. In this case, the insured is required to pay 50% of the cost until they reach the catastrophic coverage phase.