Aqueous acid P and aqueous alkali Q have equal concentrations. $20\text{ cm}^3$ of P is placed into a conical flask. Q is then added slowly to the flask, and the volume of Q together with the pH are noted. The pH titration curve is shown. Which row shows the identities of P and Q?
- AP: $\mathrm{HCl}$, Q: $\mathrm{NaOH}$
- BP: $\mathrm{H_2SO_4}$, Q: $\mathrm{NH_3}$
- CP: $\mathrm{HCl}$, Q: $\mathrm{Ba(OH)_2}$
- DP: $\mathrm{CH_3COOH}$, Q: $\mathrm{Sr(OH)_2}$