As a Bureaucratic Agency Under Direction of Congress, What Is

As a bureaucratic agency under direction of Congress, what is the purpose of the Government Accountability Office (GAO) ?

A) It manages the U.S. Treasury.
B) It is an auditing agency that investigates the actions of agencies.
C) It is an enforcement arm of Congress that prosecutes criminal activity among agency employees.
D) It acts as a liaison between the president and Congress concerning the federal budget.
E) It is an agency that lobbies Congress for favorable funding or legislation for the executive branch.