This is a real-world medical entrance exam question, please give the true answer based on the question and selection. Topic name: Biostatistics, Subject name: Social & Preventive Medicine
[{'content': 'Sampling method used in assessing immunization status of children under immunization programme is- \nSelect and explain. \nA. Systemic sampling, B. Stratified sampling, C. Group sampling, D. Cluster sampling', 'role': 'user'}, {'content': 'Answer: D \nExplanation: <p> Cluster sampling . Reference: Simple Biostatistics by Indeayan & Indrayan,1st edition,pg no:35-36 and Methods in Biostatistics by Mahajan,7 th edition,pg no:91.', 'role': 'assistant'}]