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': 'For survey of immunization by WHO age group selected is ? \nSelect and explain. \nA. 12 - 23 months, B. 0 - 6 months, C. 6 - 12 months, D. 2 - 5 years', 'role': 'user'}, {'content': "Answer: A \nExplanation: Ans. is 'a' i.e., 12 - 23 months In the Expanded programme on Immunization (EPI) cluster technique, a simplified cluster sampling method is used. It is based on ranodm selection of 210 children who are 12-23 months of age. These patients are selected in 30 clusters of 7 children each to estimate immunization coverage levels.", 'role': 'assistant'}]