TOEFL Reading: ETS-TOEFL阅读机经 - HAX754I07JYB7R9RL$

According to paragraph 5, a scientist recently visiting the Peruvian rain forest discovered that A. the specialized frequencies of the sounds made by animals are determined by their body size B. the frequencies of sounds made by animals at night are generally random C. animals and insects of particular species make sounds at specific frequencies D. animal and insect calls differ depending on whether they are heard in the laboratory or outside in nature