b
\(\begin{array}{*{20}{c}}
{\,\,\,\,\,\begin{array}{*{20}{c}}
{\,\,\,\,\,\,\,\,\,\,\,H} \\
{\,\,\,\,\,\,\,\,\,\,\,|}
\end{array}} \\
{{}^1C{H_2} = {}^2CH - {}^3C - {}^4C{H_2}Br} \\
{\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,|} \\
{\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,C{H_3}}
\end{array}\)