An electron withdrawing group (-I showing group like −NO2,−CN) stabilises the phenoxide ion, thus when present, increases the acidity of phenol. On the other hand electron releasing groups (+I showing group like −CH3,−C2H5), when present, decrease the acidity of phenol by destabilising phenoxide ion. Hence, the correct order of acidity of given compounds is (D)p-nitrophenol>(C)m-nitrophenol>(A)phenol>(B)methyl phenol (due to intermolecular H -bonding)