What Was the Chief Bureaucratic Flaw Identified by the 9/11

What was the chief bureaucratic flaw identified by the 9/11 Commission?

A) The CIA director lacked adequate access to the president.
B) There was a lack of communication between the domestic and foreign security agencies.
C) The Federal Aviation Administration was not properly monitoring all inbound airplanes on 9/11.
D) Diplomacy with the Taliban and other sponsors of terrorism had broken down in the mid-1990s.
E) The government did not act swiftly enough after the attack in order to prevent further casualties.