b
\({H_2}C = CH - C{H_2} - I\xrightarrow[{M.Rule}]{{H - I}}\) \(\mathop {\begin{array}{*{20}{c}}
{C{H_3} - CH - C{H_2}} \\
{\,\,\,\,\,\,\,\,\,|\,\,\,\,\,\,\,\,\,\,\,\,\,|} \\
{\,\,\,\,\,\,\,\,\,\,I\,\,\,\,\,\,\,\,\,\,\,I\,}
\end{array}}\limits_{(unstable)} \xrightarrow{{( - {I_2})}}\) \(C{H_3} - CH = C{H_2}\xrightarrow[{M.Rule}]{{H - I}}\begin{array}{*{20}{c}}
{C{H_3} - CH - C{H_3}} \\
{|\,\,\,\,} \\
{I\,\,\,\,}
\end{array}\)