In Baeyer's process for purifying bauxite, which description is correct?

1. A$\mathrm{Al}{}_2\mathrm{O}{}_3$ dissolves in conc. NaOH as $[\mathrm{Al}(\mathrm{OH}){}_4]{}^{-}$ leaving $\mathrm{Fe}{}_2\mathrm{O}{}_3$ as red mud; $\mathrm{CO}{}_2$ then precipitates $\mathrm{Al}(\mathrm{OH}){}_3$, which is ignited to $\mathrm{Al}{}_2\mathrm{O}{}_3$
2. B$\mathrm{Fe}{}_2\mathrm{O}{}_3$ dissolves in NaOH as ferrate and $\mathrm{Al}{}_2\mathrm{O}{}_3$ remains as the residue
3. C$\mathrm{Al}{}_2\mathrm{O}{}_3$ dissolves as $\mathrm{Al}{}^{3+}$ and excess NaOH precipitates $\mathrm{Al}(\mathrm{OH}){}_3$
4. D$\mathrm{Al}{}_2\mathrm{O}{}_3$ is reduced by NaOH to Al metal, which is then oxidised by $\mathrm{CO}{}_2$