What Did a Congressional Joint Study by the House Committees

What did a congressional joint study by the House Committees on Transportation and Infrastructure and Oversight and Government Reform in 2011 conclude about flying?

A) Flights are very susceptible to mid-air hijackings when they turn because they are forced to slow down.
B) Nothing can be done to prevent terrorism on air planes; when one security hole is patched, another quickly presents itself.
C) People have become more wary of Middle Eastern individuals and are more likely to start fights with them on planes.
D) Flying is no safer than it was before 9/11.