Which statement is true regarding Medicare's coverage?

The statement that Medicare is a federal program primarily for elderly and disabled individuals is indeed accurate. Medicare was established to provide health coverage primarily for individuals aged 65 and older, though it also extends to younger individuals with disabilities and certain conditions, such as end-stage renal disease or amyotrophic lateral sclerosis (ALS). This broad eligibility confirms Medicare's foundational purpose as a support system for vulnerable populations, ensuring necessary medical care regardless of financial status, as long as they meet the age or disability criteria.

Other options do not accurately represent the scope of Medicare. While Medicare does encompass preventive care services, it is not its primary focus, and thus option A is not entirely accurate. The program is also not limited to low-income older adults, which makes option C misleading, as enrollment is based on age or disability rather than income. Finally, while some beneficiaries opt for additional private insurance to cover costs not included in Medicare, such as copayments or deductibles, it is not a requirement for all users. Therefore, option D does not reflect the standalone availability of Medicare coverage.