i want to know..
what is the minimum nvidia graphic for playing this game with no lag

please reply for me!!
its really important!!!

Well instead of asking it that way, why not post some of your system specs and well tell you how it is likely to run.
And when you say lag free how many fps are you looking for? I would consider you mean around 40+ which is acceptable (unless of course you're playing a shooter, when you shouldn't really drop below 60.)
Please post some system specs so we can help you with this question.
If I had to take a stab at it, and at this point I do, I'd say going much below an 8800gt won't do the job.
I fully expect to see people flame this post with their systems with a lesser card that is running fine. Before you waste your time I'll go on to say that I'm running on an 8800gt (overclocked) on 1680x1050 with maxed settings and I get a pretty decent frame rates. No need to come here talking about your ancient agp card is somehow slugging through the quagmire of extensive textures that is AC.
Sorry lost my train of thought.
Also it depends on what kind of settings you want to be playing on. I'm sure if you're running 640x480 with all low settings you could manage with an older card but I don't think anybody really looks forward to playing that.