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: Social & Preventive Medicine
[{'content': '. A disease whose etiology is not known, the first step in the formation of hypothesis will be - \nSelect and explain. \nA. Cross sectional study, B. Descriptive epidemiology, C. Case control study, D. Cohort study', 'role': 'user'}, {'content': 'Answer: B \nExplanation: None', 'role': 'assistant'}]