Option A: tomato, curd, ant-sting
Oxalic acid is found in tomato, lactic acid in curd, and methanoic acid (formic acid) in ant-sting.
This is standard factual knowledge from the NCERT science curriculum. Methanoic acid = formic acid (found in ant/bee stings and nettle sting — but the specific pairing here: oxalic acid → tomato, lactic acid → curd, methanoic acid → ant-sting matches Option A). Note: nettle sting contains methanoic acid too, but Option A is the standard accepted answer matching all three correctly as per NCERT context.