Verified Answer :

The answer would probably be a big number of casualties.
Many innocent people would have died. It would have angered many especially the
tower was one of the American’s pride and sign of wealth. Most probably a war
would happen between the US and the Middle East

The correct answer, if you are on PLATO, would be the option stating the following:

One tower would have collapsed into the other, killing thousands and destroying a purported symbol of wealth and greed.

Hope this helps!!