Disability Insurance is primarily defined as:

Disability insurance is fundamentally designed to provide financial protection by replacing a portion of income that an individual might lose due to an illness or injury that prevents them from working. When a person experiences a medical condition that restricts their ability to perform their job, disability insurance steps in to offer essential income support, allowing them to manage their living expenses during their recovery period. This type of insurance can cover both short-term and long-term disabilities, depending on the specific policy, but its primary function focuses on reimbursing lost income rather than covering medical bills or healthcare services directly.

While coverage for healthcare services or insurance for medical bills pertains to health insurance, and short-term disability is just one aspect of disability insurance, the main purpose of disability insurance is clearly aimed at replacing lost income due to the inability to work. Therefore, the definition aligns perfectly with choice B, recognizing the income protection aspect as the primary focus of disability insurance.