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