Which of the following best describes how the pKa of an acid–base indicator relates to the pH at which its color change is observed during a titration?
a) The indicator changes color only when the solution pH is lower than its pKa.
b) The midpoint of the indicator’s color transition occurs when the solution pH is approximately equal to the indicator’s pKa.
c) The indicator undergoes its color change sharply when the solution pH is exactly one unit higher than its pKa.
d) The pKa of an indicator affects only the intensity of its color; it is not related to the pH at which the color shift occurs.