Q: On the morning of September 11, 19 terrorists hijacked how many commercial airliners scheduled to travel from the East Coast to California?

A: Four

Q: The hijackers crashed the first two planes into the Twin Towers of the WTC, and the third team succeeded in striking the Pentagon. Where did the fourth plane crash?

A: The fourth plane crashed in rural Pennsylvania

Q: What is the term for the global counterterrorist military campaign initiated by the United States following the September 11 attacks of 2001?

A: Global War on Terrorism/ War of Terror

Q: The U.S. invoked which article of the NATO to call upon allies to fight Al-Qaeda? How many times the U.S. has invoked this article?

A: Article 5; the U.S. has only invoked once to date

Q:  Regarding the 9/11 attack, one of the sites is termed Ground Zero. Which is it?

A: The World Trade Center site