In the reaction $\mathrm{MnO}{}_2+4\mathrm{HCl}\to \mathrm{MnCl}{}_2+\mathrm{Cl}{}_2+2\mathrm{H}{}_2\mathrm{O}$, the oxidising agent and the change in its oxidation state are

1. A$\mathrm{MnO}{}_2$; Mn changes from $+4$ to $+2$
2. B$\mathrm{HCl}$; Cl changes from $-1$ to $0$
3. C$\mathrm{HCl}$; H changes from $+1$ to $0$
4. D$\mathrm{MnO}{}_2$; Mn changes from $+2$ to $+4$