Final answer:
Minutes after the first plane hit the North Tower of the World Trade Center, the South Tower was hit, confirming the events of 9/11 as a coordinated terrorist attack.
Step-by-step explanation:
The question refers to the tragic events of September 11, 2001. Only a few minutes after the first plane hit the North Tower of the World Trade Center, specifically at 9:03 a.m., the South Tower was hit by a second hijacked airliner, United Airlines Flight 175. This second collision confirmed that the events were not just a horrific accident, but rather a coordinated terrorist attack. The other events mentioned, such as the attack on the Pentagon and the crash in Pennsylvania, occurred later in the timeline of that day's events.