Phenol is less acidic than  

I. Ethanol

II. o-nitrophenol 

III. o-methylphenol

IV. o-methoxyphenol 

This is a multiple choice answer as classified in NCERT Exemplar

(IV) o-methoxy phenol

The stability of the conjugate base  determines the acidic character of the compound.  Higher the stability of the conjugate base, the higher is the acidic character.

Phenol, O-nitrophenol, O-methyl phenol, and O-me