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': 'About direct standardization all are true except - \nSelect and explain. \nA. Age specific death rate is not needed, B. A standard population is needed, C. Population should be comparable, D. Two populations are compared', 'role': 'user'}, {'content': 'Answer: A \nExplanation: None', 'role': 'assistant'}]