The correct answer is A. is a measure of the hydrogen ion concentration.
Step-by-step explanation:
The pH determines how acid or alkaline a substance is, usually by classifying substances and mainly solutions on a scale from 0 to 14, in which 7 represents a neutral substance. This property is determined based on the hydrogen ion concentration, in this way a substance with a high hydrogen ion concentration is more acid that one with a low hydrogen ion concentration. Additionally, in this scale solutions are classified as acidic if they have a pH lower than 7 or as basic if the pH is higher than 7. According to this, it can be concluded pH is a measure of the hydrogen ion concentration.