I would definately pick A).

-because im going to be the aggressor,

But if he (and ONLY if he) came back within 1-2 seconds all in, I know hes got something, (could be pockets that made a set on the flop).

or he could have 2 pair A x suited.

I've found from my experience that it is almost impossible to put a guy on a set after the flop, I would feel comfortable as long as he didn't push his whole stack in (early in tourney, he/she is going to be thinking about survival unless they flop the nuts)...

It's one of those judgements you have to make at the table based on the feel of the game.
IMO