Which best explains how the structure of the office of the president helps fulfill the office’s role?

(A) The office is led by the chief of staff, who serves as a key adviser to the president.
(B) The office has multiple levels of staff and advisers who help the president in many areas.
(C) The office is led by the vice president, who serves as a key adviser to the president.
(D) The office has a single level of staff and advisers who help the president in many areas.