The diagram shows the apparatus used to extract aluminium by electrolysis. Which equation shows the reaction at the anode?
- A$\text{O} + 2e^- \rightarrow \text{O}^{2-}$
- B$2\text{O}^{2-} \rightarrow \text{O}_2 + 4e^-$
- C$\text{Al}^{3-} \rightarrow \text{Al} + 3e^-$
- D$\text{Al}^{3+} + 3e^- \rightarrow \text{Al}$