Electrolytic reduction cell used for conversion of calcined Al$2$O$3$ to Al is a carbon lined furnace operating at $800-900$ C$.$ The purpose of electric current supplied to the furnace is to

Achieve very high purity of aluminium $(99\mathrm{.}9\%)$

Keep the electrolyte in liquid condition by the generation of heat

Electrolytically dissociate alumina

Both $($B$)$ & $($C$)$