[chief444]

A chop is another possibility. But that doesn't really matter.

I agree it's KK or QQ. I think the fact that he checked the river makes KK much more likely. Keep in mind that he doesn't know if you hold AA and if he holds QQ he should be very concerned that you would check the river because KK would almost always check and AA might also.

I can't really see KK or AA check/raising either so I won't argue with anyone saying bet and fold to a raise. But even if you call a raise I think the fact that he checked the river makes this a pretty good bet.

Also, he probably considers that you could have JJ and would raise the river. I really don't see QQ trying to check/raise here. I think it's a pretty bad play on their part if they do.