Which of the reactions is endothermic?
- A$2\text{HBr} \rightarrow \text{H}_2 + \text{Br}_2$
- B$\text{N}_2 + 3\text{H}_2 \rightarrow 2\text{NH}_3$
- C$2\text{SO}_2 + \text{O}_2 \rightarrow 2\text{SO}_3$
- D$\text{SO}_3 + \text{H}_2\text{O} \rightarrow \text{H}_2\text{SO}_4$