An aromatic compound (a) having molecular formula C7 H7 NO2 dissolves in NaHCO3 to evolve CO2 and when reacted with NaNO2 /HCl forms (b), C7 H6 O3 . (B) dissolves in NaHCO3 and gives colour reaction with FeCl3 and can be prepared by the action of CCl4 and NaOH on phenol. When (B) is reacted with excess HNO3 , it forms (C), C6 H3 N3 O7 . (C) undergoes acetylation and decomposes NaHCO3 to evolve CO2 . On reaction with PCl5 (C) is converted to (D), C6 H5 N3 O6 Cl which when reacted with water gives back (C). Identify compounds (A) to (D).