$(a)$ $CH_3CH_2CH_2CH_2Br$
$(b)$ $\begin{matrix}
\begin{matrix}
\,\,\,\,\,\,C{{H}_{3}} \\
| \\
\end{matrix} \\
{{H}_{3}}C-C-C{{H}_{3}} \\
| \\
\,\,Br \\
\end{matrix}$
$(c)$
${CH}_{4}+{I}_{2} \underset{\text { Reversible }}{\stackrel{{hv}}{\longrightarrow}} {CH}_{3}-{I}+{HI}$