Which of the Following Chemical Equations Corresponds to the Base $\rightleftharpoons$

Which of the following chemical equations corresponds to the base ionization constant,K_b,for hydrogen sulfite ion (HSO₃^-) ?

A) HSO₃^-(aq) + H₂SO₃(aq) $\rightleftharpoons$ 2 H₂SO₃(aq)
B) HSO₃^-(aq) + H₂O(l) $\rightleftharpoons$ SO₃^2-(aq) + H₃O⁺(aq)
C) HSO₃^-(aq) + OH^-(aq) $\rightleftharpoons$ SO₃^2-(aq) + H₂O(l)
D) HSO₃^-(aq) + H₃O⁺(aq) ? H₂SO₃(aq) + H₂O(l)
E) HSO₃^-(aq) + H₂O(l) ? H₂SO₃(aq) + OH^-(aq)