What is true regarding pH levels?

The correct answer is based on the fundamental definition of pH and the relationship between hydrogen ions (H⁺) and acidity. pH is a measure of the concentration of hydrogen ions in a solution. When there is a higher concentration of hydrogen ions, the solution becomes more acidic, which is reflected in a lower pH value (below 7).

In this context, acidic solutions are characterized by an excess of H⁺ ions, leading to a sour taste and the ability to react with bases. This key concept is foundational in understanding chemical properties and behaviors of different substances in varying pH environments.

The incorrect options reflect misunderstandings of the pH scale: a higher concentration of H⁺ ions does not characterize basic or neutral solutions; rather, basic solutions have a higher concentration of hydroxide ions (OH⁻), leading to a higher pH (above 7), and neutral solutions, like pure water, have a balance of H⁺ and OH⁻ ions, resulting in a pH of approximately 7.