According to the passage, which of the following statements about body size in mammals is true? A. A large body is unfavorable to mammalian species' survival under most conditions. B. A large body tends to benefit small mammals living on islands. C. For most herbivorous mammals, a large body size is easier to sustain in the absence of large predators. D. Under most conditions, a small body is less beneficial to herbivorous mammals than to non-herbivorous mammals. E. Among non-herbivorous mammals, a small body is more beneficial on an island than on a mainland.