Chromium(III) oxide is reduced by aluminium rather than by carbon in the metallurgy of chromium. Which Ellingham-based statement supports aluminium?

1. AAluminium is a gas at the working temperature
2. BThe line of $\mathrm{Al}{}_2\mathrm{O}{}_3$ has a negative slope
3. CAt the working temperature the line of $\mathrm{Al}{}_2\mathrm{O}{}_3$ lies below the line of $\mathrm{Cr}{}_2\mathrm{O}{}_3$, so $\Delta G^{\circ }$ of $\mathrm{Cr}{}_2\mathrm{O}{}_3+2\mathrm{Al}\to \mathrm{Al}{}_2\mathrm{O}{}_3+2\mathrm{Cr}$ is negative
4. DThe line of $\mathrm{Al}{}_2\mathrm{O}{}_3$ lies above that of $\mathrm{Cr}{}_2\mathrm{O}{}_3$