I assume this is talking about the attacks on September 11, 2001.
First of all, we can use the process of elimination. We know that this fact mentions nothing about heroes, so we can eliminate D. We also know that this fact is not talking about the aftermath of the attacks, so we can eliminate C. The fact isn't really talking about the attacks, more so what lead up to the attacks.
Using the process of elimination, we were able to figure out the answer was:
a. Leading Up to the Attacks
Hope this helps you out. :)
