Sulfur Trioxide Is the Anhydride of Sulfuric Acid

Multiple Choice

Sulfur trioxide is the anhydride of sulfuric acid. However, SO₃ is not added directly to water during the synthesis of sulfuric acid because

A) hydration of SO ₃ is very exothermic and difficult to control.
B) hydration of SO ₃ is very endothermic and proceeds too slowly to be profitable.
C) at high temperatures water vapor catalyzes polymerization of SO ₃.
D) vapor phase sulfuric acid is corrosive and limits the useful life of the reactor.
E) the water would decompose under such conditions.