Which one is the most reactive towards electrophilic reagent? (AFMC 2010) (a) (b) (c) (d)

The phenolic group increases the electron density present on the benzene ring. Thus o-cresol is most reactive towards electrophilic substitution reaction. Decreasing order of activating influence is: 2 NH OH OR NHCOR Ph R Hence, the correct option is (b).