$\mathrm{Ph}-\mathrm{CH}=\mathrm{CH}_2 \xrightarrow[\text { (iii) } \mathrm{HBr}{(iv) \mathrm{Mg}, ether, then \mathrm{HCHO} / \mathrm{H}_3 \mathrm{O}^{+}}]{{(i)BH_3}{\text { (ii) } \mathrm{H}_2 \mathrm{O}_2,{ }^{\text {(-) }} \mathrm{OH}}} \mathrm{A}$
$C{{H}_{3}}CH\,=\,\,C{{H}_{2}}\,+\,\,{{H}_{2}}O\,\,+\,\,[O]\,\,\underset{Acid}{\mathop{\xrightarrow{KMn{{O}_{4}}}}}\,$$\begin{array}{*{20}{c}}
{C{H_3} - CH - C{H_2}} \\
{\,\,\,\,\,\,\,\,\,|\,\,\,\,\,\,\,\,\,\,\,\,\,|} \\
{\,\,\,\,\,\,\,\,OH\,\,\,\,\,\,\,OH}
\end{array}$ $\xrightarrow{{[O]}}{\mkern 1mu} {\mkern 1mu} X{\mkern 1mu} {\mkern 1mu} + {\mkern 1mu} {\mkern 1mu} HCOOH$
$X$ શું છે ?