The reaction below is a Bronsted-Lowry acid-base reaction.
HSO₄-(aq) + NH₃(g) → NH₄+(aq) + SO₄-(aq)

Which statement best describes the action of HSO4-(aq) in the reaction?

A. It acts as an acid because it is a proton acceptor.
B. It acts as a base because it is a proton acceptor.
C. It acts as an acid because it is a proton donor.
D. It acts as a base because it is a proton donor.