Compound 'P' on nitration with dil. HNO3 yields two isomers (A) and (B). These isomers can be separated by steam distillation. Isomers (A) and (B) show the intramolecular and intermolecular hydrogen bonding respectively. Compound (P) on reaction with conc. HNO3 yields a yellow compound 'C', a strong acid. The number of oxygen atoms is present in compound 'C' ________.