tabularx add vertical border line in merged cell

Question

I'd like to draw vertical border lines in merged cells, but now merged cells do not have any vertical border line.

How can I add lines?

\begin{table}[htbp]
\centering
\caption{policy}
\label{tab:mutationoperators}
\begin{center}
\begin{tabularx}{\textwidth}{|c|L|}
\hline
ope                 & Description               \\
\hline
\multicolumn{2}{l}{Category1 }               \\\hline
  d                       &       d                    \\\hline
\multicolumn{2}{l}{Category2}                \\\hline
                     f    &         f                  \\\hline
                       f  &         f                  \\\hline
\multicolumn{2}{l}{Category3}                \\\hline
                     f    &       f                    \\\hline
                      f   &        f                   \\\hline
\multicolumn{2}{l}{Category4}              \\\hline
                   f      &        f                   \\\hline
                   f      &        f                   \\\hline
                    f     &        f                   \\\hline
\multicolumn{2}{l}{Category5} \\\hline
                     f    &       f                    \\\hline
                     f    &        f                  \\
\hline
\end{tabularx}
\end{center}
\end{table}

Answer 1

I found a solution.

 \multicolumn{2}{|l|}{Category5} \\\hline

use \multicolumn{2}{|l|} instead of \multicolumn{2}{l}.