When Sulfur Trioxide Dissolves in Water, Sulfuric Acid Is Produced

When sulfur trioxide dissolves in water, sulfuric acid is produced.An intermediate in the reaction is H₂O-SO₃.In the reaction of the intermediate to produce sulfuric acid,

A) water acts both as an acid and a base.
B) water acts as a proton donor only.
C) water acts as a proton acceptor only.
D) the intermediate undergoes an intramolecular rearrangement to form the product.