It can be inferred from paragraph 5 and 6 that the reason Graves concluded that some of the differences between the Pacific and Atlantic enzymes were not random was that A. each of the Pacific enzymes works better in cooler waters B. the Enzymes of the Atlantic fish populations had not changed since the formation of the Isthmus of Panama C. gel electrophoresis showed that the changes benefited both the Atlantic and the Pacific fish populations D. the differences between the enzymes disappeared when the two fish populations were experimentally switched to other side of the isthmus