This is a real-world medical entrance exam question, please give the true answer based on the question and selection. Topic name: Non communicable diseases, Subject name: Social & Preventive Medicine
[{'content': 'Calendar method was described by - \nSelect and explain. \nA. Bitings, B. Ogino, C. Wallace, D. Ogive', 'role': 'user'}, {'content': "Answer: B \nExplanation: Park's textbook of preventive and social medicine 23rd edition. *safe period or rhythm method, calender method first discovered by Ogino in 1930 .the method is based on the fact that ovulation occurs from 12 to 16 days before the onset of menstruation.", 'role': 'assistant'}]