In paragraph 2, the author provides evidence for the role of biological clocks by A. listing the daily activities of an animal's cycle: sleeping, feeding, moving, reproducing, metabolizing, and producing enzymes and hormones B. describing the process of establishing the period of a biological clock C. presenting cases in which an animal's daily schedule remained stable despite lack of environmental cues D. contrasting animals whose daily schedules fluctuate with those of animals whose schedules are constant