The PKa of a Compound Whose Acidic or Basic Form

The pKa of a compound whose acidic or basic form absorbs UV or visible light can be determined spectroscopically because ________.

A) λ_max always decreases as the acidic form is converted to the basic form
B) the pKa is the same as the pH at which half of the total absorbance increase occurs
C) absorbance of the basic form is always twice that of the acidic form
D) absorbance of the acidic form is always twice that of the basic form
E) delocalization always leads to a decrease in acidity