Which of the following best describes Medicare Part D?

Medicare Part D is specifically designed to assist with covering prescription drug costs for individuals enrolled in Medicare. It provides beneficiaries access to a variety of prescription medications at reduced prices through private insurance plans approved by Medicare. This program aims to help minimize the financial burden of necessary medications and improve adherence to treatment regimens.

The other options do not accurately define Medicare Part D. Preventive services are typically covered under Medicare Part B. Inpatient hospital coverage is provided by Medicare Part A. Long-term care services are not covered under any part of Medicare, which primarily focuses on acute care and hospital services. Thus, the defining characteristic of Medicare Part D as a program for prescription drug coverage makes it the correct answer.