Share 'Three Things I (Think I) Know About 9/11'

Of the many, many things there are to know about 9/11, here are three that I hang on to.  Other suggestions are welcome.  What is not fact about 9/11 is voluminous: the Jews did it, the government did it, they hate our freedoms, etc., etc.  But here are three (proposed) facts: (1) The horror could have been prevented.  Every indication is that the government knew about Muslim men being trained to…