$C{H_3}C{H_2}OH\xrightarrow{{P + {I_2}}}A\xrightarrow[{ether}]{{Mg}} $ $B\xrightarrow{{HCHO}}C\xrightarrow{{{H_2}O}}D$
$\begin{array}{*{20}{c}}
{{C_2}{H_5}MgBr + {H_2}C - C{H_2}\xrightarrow{{{H_2}O}}} \\
{\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\backslash \,\,\,\,/} \\
{\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,O}
\end{array}A$