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.