C-08-Q190mediumsingle_mcqReaction at the anode in electrolysis of molten alumina:a2 AlX3++6 eX−→2 Al\ce{2Al^3+ + 6e- -> 2Al}2AlX3++6eX−b3 OX2−→OX2+6 eX−\ce{3O^2- -> O2 + 6e-}3OX2− (with stoichiometric balance for 2 mol O2)cAlX3+→Al\ce{Al^3+ -> Al}AlX3+dOX2+4 eX−→2 OX2−\ce{O2 + 4e- -> 2O^2-}OX2+4