Which of the following indicates a strong acidity level?

A low pH value indicates strong acidity. The pH scale ranges from 0 to 14, with values less than 7 representing acidic conditions. Specifically, the lower the pH value, the greater the concentration of hydrogen ions (H⁺) in a solution, which directly correlates with increased acidity. For example, a solution with a pH of 1 is much more acidic than one with a pH of 6. In contrast, a high pH value indicates basicness, whereas a neutral pH value (around 7) signifies that the solution is neither acidic nor basic. An unstable pH does not provide specific information about acidity or basicity and is not a standard measure of acidity. Thus, a low pH value is the clear indicator of strong acidity.