Which of the following groups is Medicare designed to cover?

Medicare is specifically designed to provide health coverage primarily to two main groups: disabled individuals and the elderly, which aligns perfectly with the correct choice. The program primarily serves people aged 65 and older but also extends benefits to individuals under 65 who have certain disabilities or conditions, such as End-Stage Renal Disease or Amyotrophic Lateral Sclerosis (ALS). This dual focus on the elderly and disabled makes this answer the most accurate reflection of Medicare's target demographic.

The other groups mentioned in the question do not align with Medicare's intended purpose. For instance, while low-income individuals may be eligible for assistance through programs like Medicaid, Medicare itself is not specifically designated for them. Children under 18 generally receive coverage through different programs like the Children's Health Insurance Program (CHIP) or Medicaid, which focus on younger populations. Additionally, limiting coverage to only individuals with chronic illnesses does not encapsulate the full scope of Medicare's eligibility, as it includes broader categories of seniors and individuals with disabilities, not just those suffering from chronic conditions.