If the pH of a solution increases from 3 to 6, what happens to its acidic nature?

Correct answer: Acidity decreases

The pH scale expresses hydrogen-ion concentration on a logarithmic scale. Values below 7 indicate acidity, and a higher pH means a lower hydrogen-ion concentration and therefore weaker acidity. A rise from pH 3 to pH 6 represents a 1000-fold decrease in hydrogen-ion concentration, although the solution remains acidic because 6 is still below 7. Thus option A is correct, while option C is false.