$(I)$ $\begin{array}{*{20}{c}}
O \\
{||} \\
{Ph\, - C - Ph}
\end{array}$
$(II)$ $\begin{array}{*{20}{c}}
{\,\,\,\,O} \\
{\,\,\,\,||} \\
{C{H_3} - C - H}
\end{array}$
$(III)$ $\begin{array}{*{20}{c}}
O \\
{||} \\
{C{H_3} - C - C{H_3}}
\end{array}$
is
$R - C \equiv N\xrightarrow[{(2)\,{H_2}O}]{{(1)\,AlH\,{{(i - Bu)}_2}}}$ ?
એસીટાલ $-$ હિમિએસીટાલ