Explanation

(d)
In the electrolytic refining of zinc, anode is made up of impure zinc while a strip of pure zinc acts as cathode. An acidified solution of zinc sulphate acts as electrolyte. When electricity is passed, following reactions occur.
At cathode
$\ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ {Zn}^{2 +} + 2e^{-} \longrightarrow Zn$
pure
At anode
$\ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ Zn \longrightarrow \ {Zn}^{2 +} + 2e^{-}$
impure