The core public health function that involves evaluating the accessibility and quality of population-based services is:

• A. Assessment.
• B. Assurance.
• C. Policy Development.
• D. Research.

Answer: (B)

Assurance focuses on making sure population-based health services are available, accessible, and of high quality, and it includes evaluating how well those services work. This function oversees service delivery, links people to needed care, ensures a skilled workforce, and—crucially—assesses the effectiveness, accessibility, and quality of the services provided. That evaluative aspect of service delivery is why it best fits the question.

Assessment is about measuring health status and needs, policy development is about shaping policies to address issues, and research is about generating new knowledge. None of these center on evaluating how accessible and how good the population-based services are.