Poker is a game of observation. Each player should be observant enough to know who bet or raised.
To have a question about a prior street be answered would violate the one-player-to-a-hand rule.
For example, player A raised, player B & C called.
On the next street, player C starts thinking, "wasn't it player A who raised? He never raises," and then asks who made the prior raise. Obviously, getting that information could affect how player C plays out the hand (and maybe even subsequent hands). That could be construed as collusion.
Bottom line: The question should not be answered by anyone.
For the record, I can't remember anyone asking about the prior street while a hand was still in play.
Current street? Sure. When asked, the simple answer, "The guy with the chips in front" is simple and obvious. And acceptable.
