Only compound (II) which has ketonic group does not form silver mirror when treated with Tollen’s reagent. Because Tollen’s reagent oxidises an aldehyde into the corresponding carboxylic acid. Ketones are not oxidised by Tollen’s reagent, so the treatment of a ketone with Tollen’s reagent in a glass test tube does not result in a silver mirror. Aldehydes give positive Tollen’s test (silver mirror test).