Which of the following equations represents the acid equilibrium associated with Ka₂ for H₃PO₃?
A) HPO₃²⁻ (aq) + H₂O (l) ⇌ PO₃³⁻ (aq) + H₃O⁺ (aq)
B) H₃PO₃ (aq) + H₂O (l) ⇌ H₂PO₃⁻ (aq) + H₃O⁺ (aq)
C) H₂PO₃⁻ (aq) + H₂O (l) ⇌ H₃PO₃ (aq) + OH⁻ (aq)
D) H₂PO₃⁻ (aq) + H₂O (l) ⇌ HPO₃²⁻ (aq) + H₃O⁺ (aq)