When a salt is heated with dilute ${\mathrm{H}}_2{\mathrm{SO}}_4$ and ${\mathrm{KMnO}}_4$ solution, the pink colour of ${\mathrm{KMnO}}_4$discharged, the salt is:

${\mathrm{KMnO}}_4$ is an oxidizer, hence salt must have an anion that can oxidise to a higher oxidation state. Salt must therefore contain sulphide $\left({\mathrm{SO}}_3^{2-}\right)$which, when oxidised with ${\mathrm{KMnO}}_4$ offer $\left({\mathrm{SO}}_4^2\right)$ (sulphate and ${\mathrm{KMnO}}_4$) himself is lowered to ${\mathrm{MnO}}_2$ e.g., the pink hue of ${\mathrm{KMnO}}_4$ discharge.