Sulfur trioxide gas combines with water to form a single product

SO3 + H2O -> ?
Based on the law of conservation of mass, which option is the product of the reaction?
A. H2SO4
B. HSO4
C. H2SO3
D. H2S2O4

A. H2SO4

In this reaction, sulfur trioxide gas (SO3) combines with water (H2O) to form sulfuric acid (H2SO4). This is the correct product based on the law of conservation of mass.