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': 'In a study to establish smoking as a risk factor for disease, 30 out of 50 smokers developed disease while as 10 out of 50 non smokers developed disease. The Odds ratio is: \nSelect and explain. \nA. 3, B. 5, C. 6, D. 10', 'role': 'user'}, {'content': 'Answer: B \nExplanation: 5', 'role': 'assistant'}]