(a)
In basic medium, the following reaction takes place
$2{KMnO}_{4} + 2KOH \longrightarrow 2K_{2}{MnO}_{4} + H_{2}O + \lbrack O\rbrack$
Due to the presence of nascent oxygen [O], ${KMnO}_{4}$ (in basic medium) behaves like an strong oxidizing agent.