$\begin{array}{*{20}{c}}
{^{C{H_3}}} \\
{_H}
\end{array}\begin{array}{*{20}{c}}
{{\text{ }}\backslash {\text{ }}} \\
/
\end{array}\mathop C\limits^{} {\mkern 1mu} = \mathop C\limits^{} {\mkern 1mu} \begin{array}{*{20}{c}}
/ \\
{{\text{ }}\backslash {\text{ }}}
\end{array}_{\mathop C\limits^{} {\kern 1pt} \equiv \mathop C\limits^{} {\kern 1pt} - \mathop C\limits^{} {\kern 1pt} {H_2}\mathop C\limits^{} {\kern 1pt} {H_3}}^H{\mkern 1mu} $
$\mathop { - CH{{(C{H_3})}_2}}\limits_1 \,\,\,\,\,\,\,\,\,\,\,\mathop { - C{H_2}C{H_2}Br}\limits_2 \,\,\,\,\,\,\,\,\,\,\mathop { - C{H_2}Br}\limits_3 \,\,\,\,\,\,\,\,\,\,\mathop { - C{{(C{H_3})}_3}}\limits_4 $
$I = II = III = IV$