In which reaction does hydrogen act as an oxidising agent?
- A$\text{H}_2 + \text{Cl}_2 \rightarrow \text{2HCl}$
- B$\text{C}_2\text{H}_4 + \text{H}_2 \rightarrow \text{C}_2\text{H}_6$
- C$\text{N}_2 + \text{3H}_2 \rightarrow \text{2NH}_3$
- D$\text{2Na} + \text{H}_2 \rightarrow \text{2NaH}$