J is a solution in water. When aqueous sodium hydroxide is added to J, a green precipitate forms. The mixture is then heated, but no gas is produced. Aluminium foil is added to the warmed mixture, and a gas is produced that changes damp red litmus paper blue. Which ions may be present in J?
- A$\text{Fe}^{3+}$ and $\text{NH}_4^+$
- B$\text{Fe}^{3+}$ and $\text{NO}_3^-$
- C$\text{Fe}^{2+}$ and $\text{NH}_4^+$
- D$\text{Fe}^{2+}$ and $\text{NO}_3^-$