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': 'Simple random sampling- \nSelect and explain. \nA. Provides least number of possible samples, B. Haphazard collection of ceain number for a sample, C. Picking every 5th or 10th at regular intervals, D. Sample represent, a corresponding strata of universe', 'role': 'user'}, {'content': 'Answer: B \nExplanation: .', 'role': 'assistant'}]