Question

Carbon is not used to reduce the oxide of aluminum to get the metal

Answer 1

Aluminium oxide is very stable andCarbon is less reactive than aluminium, thus it cannot be used to reduce aluminium oxide to aluminium metal.Aluminium are more reactive thancarbon, so it is not able to remove the oxygen from aluminium oxides. Carbonis below Al in the reactivity series

Answer 2

Aluminium is more reactive than carbon and has more affinity for oxygen than carbon.
Therefore carbon is not used to reduce the aluminium to get metal