Which of the reactions is not a redox reaction?
- A$\text{CaCO}_3 \rightarrow \text{CaO} + \text{CO}_2$
- B$2\text{C} + \text{O}_2 \rightarrow 2\text{CO}$
- C$\text{C} + \text{CO}_2 \rightarrow 2\text{CO}$
- D$\text{Fe}_2\text{O}_3 + 3\text{CO} \rightarrow 2\text{Fe} + 3\text{CO}_2$