A student has prepared a solution containing two acids: H₂A (pKa = 2.1, 7.2) and H₂B (pKa = 6.4, 10.3). If the solution is at a pH of 8.05, which combination shown below is buffering the solution?
a. HB⁻ and B²⁻
b. H₂B and HB⁻
c. HA⁻and A²⁻
d. H₂A and HA⁻