TOEFL Reading: ETS-TOEFL阅读机经 - WSI78QAYCVW5X651L$

According to paragraph 3, which of the following is NOT part of the process that the Borneo tree frog used to make its mating call heard? A. Finding a tree that has a hole of adequate size B. Immersing part of its body in a water-filled hole C. Aiming its call at a particular frog in a nearby tree D. Trying out a number of distinct call frequencies