The fluorspar (CaF2) is added in small quantities in the electrolytic reduction of alumina dissolved in fused cryolite (Na3 AlF6 ). The role of fluorspar is/areI. to decrease the rate of oxidation of carbon at anode.II. to act as a catalyst.III. to lower the temperature of the melt.IV. to make the fused mixture very conducting.     Choose the correct statement(s).