An organic compound X forms an orange yellow precipitate with 2,4-DNP reagent. It does not react with aqueous $$[Ag(NH_3)_2]NO_3$$. X on reduction with $$NaBH_4$$ gives a secondary alcohol and on oxidation with nitric acid yields a dicarboxylic acid containing the same number of carbon atoms. On bromination, X gives a monobromo product. On the basis of these reactions, it can be concluded that X
I. contains aldehydic carbonyl group                 II. contains ketonic carbonyl group
III. contains ester carbonyl group                      IV. does not contain C=C bonds