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': 'Crude bih rate is the simplest measure of feility because the denominator is ? \nSelect and explain. \nA. Total population, B. Mid-year population, C. Pre-term bihs, D. Live bih', 'role': 'user'}, {'content': "Answer: B \nExplanation: Ans. is 'b' i.e., Mid-year population", 'role': 'assistant'}]