Sulfur dioxide can be catalytically oxidised in the atmosphere by an oxide of nitrogen. Which reaction shows the catalyst being regenerated?
- A$\text{N}_2 + 2\text{O}_2 \rightleftharpoons 2\text{NO}_2$
- B$4\text{NH}_3 + 5\text{O}_2 \rightarrow 4\text{NO} + 6\text{H}_2\text{O}$
- C$\text{N}_2 + \text{O}_2 \rightarrow 2\text{NO}$
- D$\text{NO} + \tfrac{1}{2}\text{O}_2 \rightarrow \text{NO}_2$