Explanation

(c)
Calcium is obtained by electrolysis of a fused mass of $CaCl_{2}$ and KCl at about $700℃$ in an electrolytic cell made of graphite anode and iron cathode.
$\ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ CaCl_{2}\ \rightleftharpoons Ca^{2 +} + 2Cl^{-}$
At anode
$\ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ 2Cl^{-}\ \rightarrow Cl_{2} + 2e^{-}$
At cathode
$\ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ Ca^{2 +} + 2e^{-}\ \rightarrow Ca$