This is a real-world medical entrance exam question, please give the true answer based on the question and selection. Topic name: Epidemiology, Subject name: Social & Preventive Medicine
[{'content': 'In Crude death rate the population is taken as on \nSelect and explain. \nA. Ist March, B. I st July, C. Ist April, D. 15th August', 'role': 'user'}, {'content': 'Answer: B \nExplanation: Ref: Parks 23rd edition pg 57 Mid year population is considered. Hence July 1st is taken.', 'role': 'assistant'}]