a
\(\begin{array}{*{20}{c}}
O \\
{||} \\
{H - C - H}
\end{array} \,\,+ \,\, CH_3MgBr \,→ \, \begin{array}{*{20}{c}}
{\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,OMgBr} \\
| \\
{H - C - H} \\
| \\
{\,\,\,\,\,\,\,\,C{H_3}}
\end{array} \,\,\)
\( \xrightarrow{{{H_2}O/{H^ + }}} \, CH_3-CH_2-OH \, + \, Mg < \begin{array}{*{20}{c}}
{O{H^ - }} \\
{Br}
\end{array}\)