Which flask contained a supersaturated solution before the addition of nacl?

A supersaturated solution is one that contains more solute than can typically dissolve at a given temperature and pressure. In this case, the flask that contained a supersaturated solution before the addition of NaCl would be the one where the solute was present in excess, beyond its normal solubility limit. The addition of NaCl would likely cause the excess solute to precipitate out, indicating the solution was indeed supersaturated.