The correct option is D NaOH
- pH scale ranges from 0 to 14. It measures how acidic or basic a solution is.
- Acids have pH range from 0 to 7. E.g. HCl and H2SO4 have pH between 0 to 7.
- Neutral solutions have a pH value of 7. E.g. distilled water has pH 7.
- Bases have pH range from 7 to 14. E.g. NaOH solution has pH higher than 7.
- Thus, out of all options, NaOH has the highest pH.