Aluminium oxide is an extremely stable compound, far more stable than iron oxide, so heating it with carbon the way a blast furnace does for iron simply is not enough to pull the oxygen away from the aluminium. The only practical way to break this bond is to force the reduction electrically, but pure alumina melts above 2050 degrees Celsius, which would make direct electrolysis hugely expensive in energy terms. The workaround, known as the Hall-Heroult process, dissolves alumina in a molten bath of cryolite, which lowers the melting point of the mixture to around 950 to 980 degrees Celsius while still allowing current to pass through and deposit molten aluminium at the cathode. Since water-based electrolysis would let hydrogen ions discharge before aluminium ions ever could, only electrolysis of a molten alumina-cryolite mixture actually works. So the correct choice is option (B).