Which of the following reactions of $KMnO_4$ occurs in acidic medium?

Assign $A$,$B$,$C$,$D$ from given type of reaction.
$Zn_{(s)} + 2HCl_{(aq)} \longrightarrow ZnCl_{2(aq)} + H_{2(g)}$

Number of moles of $H^{+}$ ions required by $1 \ mole$ of $MnO_4^{-}$ to oxidise oxalate ion to $CO_2$ is . . . . . .

Identify the elements undergoing reduction and oxidation respectively in the following redox reaction.
$3 H_3AsO_{3(aq)} + BrO_{3(aq)}^{-} \rightarrow Br_{(aq)}^{-} + 3 H_3AsO_{4(aq)}$

Permanganate $(VII)$ ion,$MnO_4^-$,in basic solution oxidises iodide ion,$I^-$,to produce molecular iodine $(I_2)$ and manganese $(IV)$ oxide $(MnO_2)$. Write a balanced ionic equation to represent this redox reaction.

Assign $A, B, C, D$ from the given type of reaction for the following chemical equation:
$N_2 + 3H_2 \longrightarrow 2NH_3$