At what pH is [H₂PO₄-] = [HPO₄²-]? For H₃PO₄ Ka1 = 7.11 x 10⁻3, Ka2 = 6.34 x 10⁻8, and Ka3 = 4.22 x 10⁻13.
A) pH = pKa1
B) pH = pKa2
C) pH = pKa3
D) pH = (pKa1 + pKa2)/2