The short answer is Islamic terrorists.
Of course, if you live in an Islamic country and the government does not allow for a free media or you're just biased, then it's the Israelis or the US government (though, this is a popular theory amongst US democrats too).
However, I can easily show those who claim it was the Israelis or the US government are lying through their teeth and are just saying so as mere propaganda and are using something called "Island Hopping Logic."
If you ask them who brought down the Twin Towers, it was Bush or the Jews.
Ask them what they think of Osama Bin Laden and "Oh, he's our hero! Did you see what he did to the Twin Towers!"
You'd be amazed how common this is...or perhaps not.
Another thing that stuck out about this chart is our good Mexican friends to the south. Only 25% of them believe it was Islamic terrorists. Of course, that's why they were all cheering for Osama Bin Laden during a soccer match against the US.
So I don't want the world telling us who they (wink wink) "think" pulled off 9-11. You all know who did.