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': 'Probability = \nSelect and explain. \nA. Odds / (1 + adds), B. Odds / (1 - adds), C. (1 + adds) / adds, D. (1 - adds) / adds', 'role': 'user'}, {'content': 'Answer: B \nExplanation: None', 'role': 'assistant'}]