A paper ash containing the precipitate is moistened with $\mathrm{Co}(\mathrm{NO}{}_3){}_2$ and ignited. Which pair of cation and ash colour is correct?

1. A$\mathrm{Zn}{}^{2+}$ -- green; $\mathrm{Al}{}^{3+}$ -- black
2. B$\mathrm{Zn}{}^{2+}$ -- blue; $\mathrm{Al}{}^{3+}$ -- green
3. C$\mathrm{Zn}{}^{2+}$ -- green; $\mathrm{Al}{}^{3+}$ -- blue
4. D$\mathrm{Zn}{}^{2+}$ -- pink; $\mathrm{Al}{}^{3+}$ -- blue