Which is the most important and largest agency in the Executive Office of the President?

a. Office of Management and Budget.

b. National Security Council.

c. Council of Economic Advisors.

d. Council of Environmental Quality.

Answer: A - Office of Management and Budget

Explanation: The Office of Management and Budget (OMB) is the largest office within the Executive Office of the President of the United States.

OMB's most prominent function is to produce the President's Budget. It also measures the quality of agency programs, policies, and procedures to see if they comply with the president's policies and coordinates inter-agency policy initiatives.

OMB was reorganized to remove the distinction between management staff and budgetary staff by combining the dual roles into each given program examiner within the Resource Management Offices.