The reaction equations for P and Q are shown below. P: $2\text{NaNO}_2 + \text{O}_2 \rightarrow 2\text{NaNO}_3$ Q: $2\text{HgO} \rightarrow 2\text{Hg} + \text{O}_2$ For which of these reactions does oxidation of the underlined substance take place?
- AP ✓, Q ✓
- BP ✓, Q ✗
- CP ✗, Q ✓
- DP ✗, Q ✗