Assign $A$,$B$,$C$,$D$ from the given type of reaction.
$CaSO_3(s) + H_2SO_4(aq) \longrightarrow CaSO_4(s) + SO_2(g) + H_2O(l)$

$x, y$ and $z$ are respectively:
$MnO_4^- + x e^- \xrightarrow{\text{Alkaline medium}} MnO_4^{2-}$
$MnO_4^- + y e^- \xrightarrow{\text{Acidic medium}} Mn^{2+}$
$MnO_4^- + z e^- \xrightarrow{\text{Neutral medium}} MnO_2$

Given below are two statements:
Statement-$I$ : Heating $NaCl$ with concentrated $H_2SO_4$ and $MnO_2$ results in oxidation of $Mn$.
Statement-$II$ : Heating $NaI$ with concentrated $H_2SO_4$ and $MnO_2$ results in reduction of $Mn$.
In light of the above statements, choose the most appropriate answer from the options given below:

Which of the following reactants can be reduced by $SO_2$ in the given reactions?
$(I)$ $O_3 \to$ product
$(II)$ $Cr_2O_7^{2-} \xrightarrow{H^{+}} $ product
$(III)$ $MnO_4^{-} \xrightarrow{H^{+}} $ product
$(IV)$ $H_2S \to$ product

$KMnO_4$ reacts with oxalic acid according to the equation:
$2MnO_4^- + 5C_2O_4^{2-} + 16H^+ \to 2Mn^{2+} + 10CO_2 + 8H_2O$
Here $20 \ mL$ of $0.1 \ M \ KMnO_4$ is equivalent to:

$A$ given amount of $Fe^{2+}$ is oxidized by $x \ mol$ of $MnO_{4}^{-}$ in acidic medium. The number of moles of $Cr_{2}O_{7}^{2-}$ required to oxidize the same amount of $Fe^{2+}$ in acidic medium is