Correct option (b)
Explanation :
Phenol is most acidic of all the given compounds.
In phenol, the electron withdrawing phenyl ring polarizes the O - H bond thereby facilitating the release of H as H+ and hence phenol is most acidic.
the electron withdrawing effect of phenyl ring is somewhat diminished by the -CH2 group and it is therefore less acidic than phenol. In (c) and (d), -OH group is attached to alkyl groups which, due to their +I effect reduce the polarity of -OH bond and so the acidic strength is low.
