How long after the 1st Tower was the 2nd tower impacted?

The North Tower was hit at 8:46 am and collapsed at 10:28 am. The South Tower was hit at 9:03 am and collapsed at 9:59 am. The resulting debris severely damaged or destroyed more than a dozen other adjacent and nearby structures, ultimately leading to the collapse of Seven World Trade Center at 5:21 pm.

Explanation:

your answer would be (a)