In the above chemical reaction sequence " A " and " B " respectively are

$\displaystyle \mathrm{H}_2 \mathrm{O}, \mathrm{H}^{+}$and $\displaystyle \mathrm{KMnO}_4$

$\displaystyle \mathrm{O}_3, \mathrm{Zn} / \mathrm{H}_2 \mathrm{O}$ and $\displaystyle \mathrm{NaOH}_{(\text {alc })} / \mathrm{I}_2$

$\displaystyle \mathrm{H}_2 \mathrm{O}, \mathrm{H}^{+}$and $\displaystyle \mathrm{NaOH}_{(\mathrm{alc})} / \mathrm{I}_2$

$\displaystyle \mathrm{O}_3, \mathrm{Zn} / \mathrm{H}_2 \mathrm{O}$ and $\displaystyle \mathrm{KMnO}_4$