The Reaction in Which Water and Carbon Dioxide Combine to Form

The reaction in which water and carbon dioxide combine to form carbonic acid is

A) irreversible, as carbonic acid rapidly causes a drop in pH.
B) reversible, and can proceed in either direction depending on the concentrations of the molecules.
C) exergonic, and is an important energy source within the body.
D) an exchange reaction in which protons are transferred between atoms.
E) a catabolic reaction in which the formation of a larger molecule can lead to an increase in cell size.