TOEFL Reading: ETS-TOEFL阅读机经 - 9LM0572G75T4DHB5L$

Which of the sentences below best expresses the essential information in the highlighted sentence in the passage? Incorrect choices change the meaning in important ways or leave out essential information. A. Group living allows some animals to transcend problems of habitat. B. Group living is only advantageous when benefits outweigh inevitable problems. C. Problems resulting from living socially extend beyond the habitat. D. It is difficult to determine whether the benefits of social living offset its costs.