Aluminium is obtained by electrolysis, as illustrated. Which row gives the ionic half-equations at the cathode and at the anode?
- Acathode: $\text{Al}^{3+} \rightarrow \text{Al} + 3\text{e}^-$ ; anode: $2\text{O}^{2-} \rightarrow \text{O}_2 + 4\text{e}^-$
- Bcathode: $\text{Al}^{3+} \rightarrow \text{Al} + 3\text{e}^-$ ; anode: $2\text{O}^{2-} + 4\text{e}^- \rightarrow \text{O}_2$
- Ccathode: $\text{Al}^{3+} + 3\text{e}^- \rightarrow \text{Al}$ ; anode: $2\text{O}^{2-} \rightarrow \text{O}_2 + 4\text{e}^-$
- Dcathode: $\text{Al}^{3+} + 3\text{e}^- \rightarrow \text{Al}$ ; anode: $2\text{O}^{2-} + 4\text{e}^- \rightarrow \text{O}_2$