Which chemical equation represents an oxidation reaction?
- A$\text{CaCO}_3 \rightarrow \text{CaO} + \text{CO}_2$
- B$4\text{FeO} + \text{O}_2 \rightarrow 2\text{Fe}_2\text{O}_3$
- C$2\text{NO}_2 \rightarrow \text{N}_2\text{O}_4$
- D$2\text{P}_2\text{O}_5 \rightarrow \text{P}_4\text{O}_{10}$