The Hydrogen Sulfate or Bisulfate Ion HSO₄^- Can Act as Either

The hydrogen sulfate or bisulfate ion HSO₄^- can act as either an acid or a base in water solution.In which of the following equations does HSO₄^- act as an acid?

A) HSO₄^- + H₂O $\to$ H₂SO₄ + OH^-
B) HSO₄^- + H₃O⁺ $\to$ SO₃ + 2H₂O
C) HSO₄^- + OH^- $\to$ H₂SO₄ + O^2-
D) HSO₄^- + H₂O $\to$ SO₄^2- + H₃O⁺
E) none of these