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': 'Denominator of crude birth rate is \nSelect and explain. \nA. Number of death children, B. Number of living children, C. Mid year population, D. Total number of crude birth', 'role': 'user'}, {'content': 'Answer: C \nExplanation: None', 'role': 'assistant'}]