While hydration and dehydration of carbon dioxide occur spontaneously, carbonic anhydrases are necessary as a.spontaneous hydration and dehydration of carbon dioxide occur very slowly. b.spontaneous hydration and dehydration of carbon dioxide are rapid, but not at speeds necessary for biochemical processes, and hydration and dehydration of carbon dioxide are sometimes coupled to other biochemical processes. c.hydration and dehydration of carbon dioxide are sometimes coupled to other biochemical processes. d.spontaneous hydration and dehydration of carbon dioxide are rapid, but not at speeds necessary for biochemical processes. e.spontaneous hydration and dehydration of carbon dioxide occur very slowly, and hydration and dehydration of carbon dioxide are sometimes coupled to other biochemical processes