This indicates
the presence of unsaturation due to an aromatic ring Compound (B), being an oxidation product of a ketone should be a
carboxylic acid The molecular formula of (B) indicates that it should
be benzoic acid and compound (A) should, therefore, be a
monosubstituted aromatic methyl ketone The molecular formula of
(A) indicates that it should be phenyl methyl ketone (acetophenone)