Answer: B. The U.S. war in response to the attack on 9/11 caused chaos in the Middle East, which contributed to the rise of ISIL.
Explanation:
After the 9/11 attacks, the United States began its war on terror that was focused mainly in the Middle East. The chaos and destabilization that followed especially in Iraq and compounded by the events of the Arab spring, allowed Islamic State of Iraq and the Levant (ISIL) to rise.
Indeed it is worthy of note that one main reason ISIL was able to rise so quickly was because the former allies and advisors to Saddam Hussein who was deposed by the US, aided them both militarily and financially both of which went a long way in building ISIL to what it was.