Hi there!
The answer is:
C) The Constitution makes the President the chief administrator of the Federal Government.
But the Presidency office not only includes the representative President but the rest of the executive branch of the U.S. government, and it is the only "office" that is elected nationally.
The President is at the top of the Federal Bureaucreacy due to the Constitution although this is not deeply mentioned. The Article II establishes the office and states that the executive power shall be vested in a President of the United States of America, but the President's decisions towards the country will only be valid with the advice and consent of the Senate.