In which equation does the underlined reactant behave as a base?
- A$\text{CH}_3\text{COO}^- + \underline{\text{H}_3\text{O}^+} \rightarrow \text{CH}_3\text{COOH} + \text{H}_2\text{O}$
- B$\underline{\text{NH}_4^+} + \text{OH}^- \rightarrow \text{NH}_3 + \text{H}_2\text{O}$
- C$\text{CO}_2 + 2\underline{\text{H}_2\text{O}} \rightarrow \text{H}_3\text{O}^+ + \text{HCO}_3^-$
- D$\underline{\text{H}^+} + \text{OH}^- \rightarrow \text{H}_2\text{O}$