TOEFL Reading: ETS-TOEFL阅读机经 - 49U3734W41C6JC3DL$

The author provides information about "the visual modality" in order to A. emphasize that visual information plays a significant part in frog breeding B. explain why some frogs breed at night, while others breed during the day C. indicate the resourcefulness with which frogs overcome obstacles in sound travel during the breeding process D. argue that auditory signals have advantages over visual signals for frog reproduction