The table gives the pH values for several substances that humans can eat or drink. Substances and pH values: $P: 6.6$, $Q: 3.1$, $R: 10.4$, $S: 7.8$ Which statement about these substances is true?
- AP is alkaline.
- BQ has the lowest concentration of hydrogen ions.
- CR can neutralise excess stomach acid.
- DS has a pH value closest to neutral.