How to name this benzene alcohol?
The compounds given in the question contain the characteristic group $(\ce{-OH})$. Since there is only one characteristic group, the seniority order of classes is not relevant in this case; thus, the $\ce{-OH}$ substituent corresponds to the principal characteristic group that is expressed as a suffix (‘ol’).

Therefore, the preferred IUPAC name (PIN) for compound (e) is benzene-1,2,4-triol.



Various traditional names exist for hydroxy compounds. According to the current version of Nomenclature of Organic Chemistry – IUPAC Recommendations and Preferred Names 2013 (Blue Book), only the name ‘phenol’ is retained as a PIN.


  P-63.1.1.1 Only one name is retained, phenol, for $\ce{C6H5-OH}$, both as a preferred name and for general nomenclature. The structure is substitutable at any position. Locants 2, 3, and 4 are recommended, not o, m, and p.


Therefore, the PIN for compound (c) is indeed phenol.



Furthermore, according to Subsection P-63.1.1.2, the names


pyrocatechol (benzene-1,2-diol),
resorcinol (benzene-1,3-diol), and 
hydroquinone (benzene-1,4-diol)


are retained but only for general nomenclature and only when unsubstituted.

Therefore, the PIN for compound (d) is the systematic name benzene-1,2-diol (the traditional name ‘pyrocatechol’ may be used in general nomenclature).