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': 'People are separated into groups, from each group people are selected randomly. What type of sampling is this - \nSelect and explain. \nA. Simple random, B. Stratified random, C. Systemic random, D. Cluster', 'role': 'user'}, {'content': 'Answer: B \nExplanation: None', 'role': 'assistant'}]