Explanation:

- The Employees' State Insurance Act, 1948, outlines the authority responsible for evaluating disablement issues in insured persons.

- Option 1: The Insurance Medical Practitioner - This role involves treating and assessing patients but not determining disablement.

- Option 2: The Social Security Officer - Focuses on administrative roles rather than medical assessments.

- Option 3: The Medical Board - Correct authority tasked with determining questions relating to disablement under the Act.

- Option 4: The Medical Appeal Tribunal - Deals with appeals concerning medical decisions but is not the initial authority for determining disablement.