List-1	List-2
(A) ${Cr}_2{O}_7{}^{2-}⟶{Cr}^{3+}$	(1) 2 electrons are required
(B) $C_2{O}_4{}^{2-}⟶{CO}_2$	(2) 1 electrons are required
(C) ${ClO}^{-}⟶{ClO}_3^{-}$	(3) 5 electrons are required
(D) ${MnO}_4^{-}⟶{MnO}_4{ }^{2-}$	(4) 4 electrons are required
	(5) 6 electrons are required

The correct match is

The oxidation state of chromium in ${Cr}_2{O}_7{ }^{2-}$ is $+6$ and in ${Cr}^{3+}$ is $+3$, the change in oxidation state is $+3$ there are $2$ chromium atoms and hence $6$ electrons are required for reduction

The oxidation state of carbon in $C_2{O_4}^{2-}$ is $+3$ and in ${CO}_2$ is $+4$, the change in oxidation state is $+1$ there are $2$ carbon atoms and hence $2$ electrons are involved in oxidation

The oxidation state of chlorine in ${ClO}^{-}$is $+1$ and in ${ClO}_3^{-}$is $+5$, the change in oxidation state is $+4$ and hence $4$ electrons are involved in oxidation

The oxidation state of manganese in ${MnO}_4^{-}$is $+7$ and in ${MnO}_4{ }^{2-}$ is $+6$, the change in

oxidation state is $+1$ and hence $1$electrons are involved in oxidation

Hence the correct option is $\left(A\right)$.