Consider a solution consisting of the following two buffer systems: H2CO3 HCO3– + H+ pKa = 6.4 H2PO4– HPO42– + H+ pKa = 7.2 At pH 6.4, which one of the following is true of the relative amounts of acid and conjugate base present? A) [H2CO3] > [HCO3–] and [H2PO4–] > [HPO42–] B) [H2CO3] = [HCO3–] and [H2PO4–] > [HPO42–] C) [H2CO3] = [HCO3–] and [HPO42–] > [H2PO4–] D) [HCO3–] > [H2CO3] and [HPO42–] > [H2PO4–] E) [H2CO3] > [HCO3–] and [HPO42–] > [H2PO4–]