Which of the following is a national health insurance program covering the elderly?

Medicare is a national health insurance program specifically designed to provide coverage for individuals aged 65 and older, as well as for certain younger individuals with disabilities or specific diseases. The program is funded primarily through payroll taxes, premiums, and government funding, ensuring that elderly individuals have access to a wide range of health services, including hospital care (Part A), medical insurance (Part B), and prescription drug coverage (Part D).

Medicaid, while also a health insurance program, primarily serves low-income individuals and families rather than focusing specifically on elderly coverage. Tri-Care is a health care program specifically for military personnel, veterans, and their dependents, which is not geared towards the general elderly population. Social Security provides financial support for retired individuals but does not offer health insurance coverage. Therefore, Medicare stands out as the correct answer because of its targeted services specifically for the elderly population.