Dilute $\mathrm{HCl}$ is not used to acidify a $\mathrm{KMnO}{}_4$ titration because:

1. A$\mathrm{HCl}$ is a weak acid and gives too few $\mathrm{H}{}^{+}$ ions
2. B$\mathrm{Cl}{}^{-}$ precipitates $\mathrm{Mn}{}^{2+}$ as $\mathrm{MnCl}{}_2$
3. C$\mathrm{HCl}$ reduces $\mathrm{KMnO}{}_4$ only to $\mathrm{MnO}{}_2$
4. D$\mathrm{KMnO}{}_4$ oxidises $\mathrm{Cl}{}^{-}$ to $\mathrm{Cl}{}_2$, consuming extra permanganate