Answer:
A. Several U.S airliners were taken over by terrorists
Explanation:
"On September 11, 2001, 19 militants associated with the Islamic extremist group al Qaeda hijacked four airplanes. Two of the planes were flown into the twin towers of the World Trade Center in New York City, a third plane hit the Pentagon in Arlington, Virginia, just outside Washington, D.C., and the fourth plane crashed in a field in Shanksville, Pennsylvania"
