Electrolytic reduction of `Al_(2)O_(3)`.
Electrolyte (`Al_(2)O_(3)+"cryolite")`
Anode: Graphite rods.
Coke powder is spreadded over the molten electrolyte due to
A. Prevent the loss of heat radiation from the surface
B. prevent corrosion of graphite
C. prevent oxidation of molten aluminium by air
D. (a) both (b)
