In the following question, a situation is described followed by a list of words. Identify the correct word that can be used to describe the passage/ a part of the passage and mark the answer accordingly.

The deaths of approximately 3,000 people in the suicidal collision of hijacked commercial airliners into the World Trade Center and the Pentagon on 11 September 2001 was the most destructive terrorist attack recorded in world history which resulted in untold misery and suffering. This very atrocious act was committed at a time when experts had been defining a new form of international terrorism which states that not even a superpower like America is immune from these attacks as the main objective behind this mass destruction.