Question
Which is correct ?




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$\begin{array}{*{20}{c}}
{R = - CH - Cl}\\
{|\,\,}\\
{\,\,\,\,C{H_3}}
\end{array}\,\,\,\,,\,\,\,\,\,\,\,\,\,\,\begin{array}{*{20}{c}}
{S = - CH - Cl}\\
{|\,\,}\\
{Br}
\end{array}$
$(a)$ ${CrO}_{3}$ $(b)$ ${Fe}_{2} {O}_{3}$ $(c)$ ${MnO}_{2}$ $(d)$ ${V}_{2} {O}_{5}$ $(e)$ ${Cu}_{2} {O}$

