According to paragraph 3, what evidence suggests that extreme development of the auditory system may be the primary reason for the dolphin's large brain? A. Other odontocetes with highly developed auditory systems also have large brains B. Social animals, such as dolphins, require highly developed auditory systems, which tend to be associated with large brains C. The echolocation system used by dolphins is possible only with a highly developed auditory system and a correspondingly large brain D. The auditory regions of dolphins' brains are much larger than those of human brains