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: Medicine
[{'content': 'Female menstrual cycle is diagnosed by \nSelect and explain. \nA. Sex steroid profile, B. Basal body temperature, C. Vaginal cell cytology, D. Cervical mucus test', 'role': 'user'}, {'content': 'Answer: A \nExplanation: None', 'role': 'assistant'}]