In the above sequence of reactions, A and D, respectively, are:

$\mathrm{KI}$ and $\mathrm{KMnO}_{4}$

$\mathrm{MnO}_{2}$ and $\mathrm{KIO}_{3}$

$\mathrm{KIO}_{3}$ and $\mathrm{MnO}_{2}$

$\mathrm{KI}$ and $\mathrm{K}_{2} \mathrm{MnO}_{4}$