#1 and #3 for me. I remember always being irregularly shy, even more so than any other students in my elementary class, and then it was all made worse in middle school when bad things started to happen.
I had anxiety before - generalized, which I would say was upbringing. My parents were somewhat more strict with me than my brother. They kind of learned their lesson with me by the time my brother was born 4 1/2 years later.
My current episode of SA started through peer humilation in an abusive church - they used their sermons to "indirectly" vent members' issues in the church - they tried to kick me out on two different occasions without even giving me an official reason. I had SA and was so frightened of them at the time that I went to church to pray for healing! THey saw me as a monster that needed excommunication - all I did was have trouble talking to people!
No one in my family has SA, other than me. My mum is kind of shy, so is my brother, but in no way do they have SA.
On the other hand, my dad and sister are both extremely outgoing -- my dad is the most outgoing person I've ever met; he'll talk quite comfortably to anyone and seems at ease in any situation.
I think there is a genetic predisposition to anxiety, but it's a series of events and circumstances that account for its severity in my case. So I'll say it's a combination of the first three.
I dunno, I wasn't abused in any way. My father and brothers are very outgoing, so I have to assume there is some amount of predisposition. But my mother is pretty quiet and shy, so maybe, for whatever reason, I learned from that and my brothers didn't.