Correct Option (b) IV > III > I > II
Explanation:
Acidic due to resonance stabilisation of phenoxide ion.
NO2 withdraws electrons, stabilises the phenoxide ion, hence acidity is increased.
(iv) Lower acidity in case of meta-isomer as compared to para-isomer is explained by the fact that m-nitrophenoxide is stabilised by inductive effect only and no resonance effect operates with -NO2 group.
Thus, m-nitrophenol < p-nitrophenol (acidic)
(iii) (iv)
Thus, correct order is iv > III > I > III