Phenyl is an electron withdrawing substituent while $-C H_{3}$ is an electron releasing substituent.
Moreover, phenoxide ion is more resonance stabilised as compared to benzyloxide ion, thus releases proton more easily. That's why phenol is a strong acid among the given compounds
$\begin{array}{*{20}{c}} {C{H_2}OH} \\ {|\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,} \\ {C{H_2}OH} \end{array}$ $+$ ઓક્ઝેલિક ઍસિડ $\xrightarrow{{{{210}^o}C}}$ $\quad\quad X$
$\quad\quad\quad\quad\quad\quad\quad\quad\quad\quad\quad\quad\quad\quad$(મુખ્ય નીપજ)