(A) They were funded by OBL and his backers, through Al-Qaeda's own funds.
...although I believe the tentacles stretched pretty wide. His anti-western message resonated with a lot of peoples who had suffered under colonial policies; people who didn't want their own cultures changed to match Western culture (whether or not we think this is wrong, they didn't want change forced on their culture any more than we Americans want to suddenly be coerced into becoming 10th century Buddhist monastics.
(A) He was an active member of Al-Qaeda, and was at the last moment considered to be a substitute terrorist involved in the 9/11 attacks, but this was not carried through.
I also think that OBL and other Al-Qaeda cell leaders thought he was a real loose cannon. I would not be surprised if they used this as a subtle way of trying to get rid of him.
My answers: they were all aboard the planes and were all killed in the crashes. The military did not shoot any of them down.
(E) There were signs and warnings that could have been put together IF various agencies weren't playing "island empire." I think that the Bush administration did little to encourage them to work together. Nor was Bush interested in learning what the Clinton administration had. I think he was too involved in doing a "victory lap" and going off to bask in his new importance at his Crawford ranch (a pattern that he followed, by the way, as governor of Texas.)
(D) Other (Please explain). I'm not sure I can adequately convey my contempt for this view.
(A) 19 Hijackers, most of middle eastern origin, hijacked AA11 and UA175 and proceeded to purposely fly these planes into the WTCs on 9/11 to attack the USA.
Also factoring into it was the impact of the collapse of floors above... see Richard Muller's paper for this (the "physics for future presidents" professor at UCLA Berkeley)
I think that the people with this theory have never actually been near a collapsing building, have no notion of how sound echoes and reverberates off buildings, have probably watched only videos of controlled demolitions, and know nothing about sound and sound quality and recording.
Bad Science. VERY bad science. There weren't any steel framed skyscrapers of that height collapsing from any force prior to 9/11. Extrapolating from a sample set of zero doesn't give any truth.
As to who gives the best version, try Richard Muller:
http://muller.lbl.gov/teaching/Physics10/old physics 10/chapters (old)/3-The_terrorist_attack.htm
