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': 'In MCH programme the sampling is done by which method – \nSelect and explain. \nA. Systemic, B. Stratified, C. Group, D. Cluster–30', 'role': 'user'}, {'content': 'Answer: D \nExplanation: None', 'role': 'assistant'}]