TOEFL Reading: ETS-TOEFL阅读机经 - 3NFRMDHS618392G7L$

According to paragraph 4, what is true about bottlenose dolphin societies? A. There is far more cooperation than competition among individuals B. Long-term social relationships tend to exist primarily between individuals of the same sex and similar ages. C. They are similar to chimpanzee societies in terms of the types of social relationships that exist. D. They are far more complex than the societies of any other species of odontocetes