To an acid solution of an anion, a few drops of ${\mathrm{KMnO}}_4$ solution are added. Which of the following, if present will not decolourise the ${\mathrm{KMnO}}_4$ solution

An acid solution of an anion the element that will not decolourise the ${\mathrm{KMnO}}_4$ solution from the given options.The maximam oxidation state of C in ${\mathrm{CO}}_3^{-2}$ is +4. As a result, it has no inclination to oxidise and will not be able to decrease ${\mathrm{KMnO}}_4$. As a result, the ${\mathrm{KMnO}}_4$ solution will not be decolourised.