From his experiments, S.L. Miller produced amino acids by mixing which of the following in a closed flask:

1. ${\mathrm{CH}}_3,$ ${\mathrm{H}}_2,$ ${\mathrm{NH}}_4$ and water vapour at $800°\mathrm{C}$

2. ${\mathrm{CH}}_4,$ ${\mathrm{H}}_2,$ ${\mathrm{NH}}_3$ and water vapour at $600°\mathrm{C}$

3. ${\mathrm{CH}}_3,$ ${\mathrm{H}}_2,$ ${\mathrm{NH}}_3$ and water vapour at $600°\mathrm{C}$

4. ${\mathrm{CH}}_4,$ ${\mathrm{H}}_2,$ ${\mathrm{NH}}_3$ and water vapour at $800°\mathrm{C}$