The correct answer is:
A. To manage the executive office of the president and advise the president
Step-by-step explanation:
The President's Chief of Staff is the leader of the Executive Office of the President, this position was created by President Franklin Roosevelt in 1939.
The President's Chief of Staff role is to act as an Assistant to the President, to select and supervise the staff in the Executive Office (White House), to select the information flow that gets to President's desk, as well as who gets to speak with him, to manage the daily activities of the President, to give advice and to protect the interests of the President.