Which statement correctly describes the extraction of aluminium by electrolysis?
- AAluminium oxide is dissolved in molten cryolite to increase its melting point.
- BAt the cathode, oxygen ions lose electrons to form oxygen gas.
- CThe carbon in the graphite anode reacts with oxygen gas forming carbon dioxide.
- DThe reaction at the anode is $\mathrm{Al^{3+}} + 3e^{-} \rightarrow \mathrm{Al}$.