CORRECT answer is Oxalic acid. ACIDPRESENT INMethonic acidStinging ants, Nettles, Pine NEEDLES, Sweat.Oxalic acidLeafy GREENS, Vegetables, Fruits, Cocoa, Nuts, Seeds , tomatoesTartaric AcidTamarind, GrapesAscorbic AcidOranges, BRUSSELS SPROUTS, Cauliflower, BroccoliAcetic AcidVinegar, Pickled vegetables