Answer
$O_{2}(g) + 4H_{2}O(aq) + 4e^{-} → 2H_{2}O (l) + 4OH^{-}$
This is a reduction reaction
Work Step by Step
We add water to left hand side and OH- to right hand side to balance the equation as it is in basic medium. Since oxidation state of Oxygen changes from 0 to -2, this is a reduction reaction.