In which reaction is the first substance in the equation oxidised?
- A$\text{CaO} + \text{H}_2\text{O} \rightarrow \text{Ca(OH)}_2$
- B$4\text{FeO} + \text{O}_2 \rightarrow 2\text{Fe}_2\text{O}_3$
- C$\text{SnO}_2 + 2\text{H}_2 \rightarrow \text{Sn} + 2\text{H}_2\text{O}$
- D$\text{ZnCO}_3 \rightarrow \text{ZnO} + \text{CO}_2$