This is a real-world medical entrance exam question, please give the true answer based on the question and selection. Topic name: None, Subject name: Physiology
[{'content': 'Changes in biological activity occurring daily are\nreferred as  __________ rhythm: \nSelect and explain. \nA. Circadian, B. Circa triginatan, C. Circa sestin, D. Circannual', 'role': 'user'}, {'content': 'Answer: A \nExplanation: None', 'role': 'assistant'}]