Which of the following phrases best describes the relationship between the attacks on 9/11 and ISIL?

The answer is "Option b".

Explanation:

It is the only link between the 9/11 incident as well as the attack through ISIL would be that ordinary citizens lost their lives without reason for both attacks. Its difference, however, would be that the September 11 attacks were a terror act, and nearly 3000 innocent people were killed.  

Even so, ISIL is indeed a terror group, extremely active throughout the Middle East, particularly Iraq, murdering innocent civilians in behalf of Jihad, but security personnel from around the world, and particularly US forces, who are striving to eradicate them and to ensure peace prevails in the region.