b
(b) $\begin{array}{*{20}{c}}
{\begin{array}{*{20}{c}}
{C{H_2} - OH} \\
{|\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,}
\end{array}} \\
{CH - OH\,\,} \\
{|\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,} \\
{C{H_2} - OH}
\end{array}$
one secondary and two primary alcoholic groups.