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': 'Confidence limit is calculated by - \nSelect and explain. \nA. Mean and standard error, B. Mean and standard detion, C. Median and standard detion, D. Median', 'role': 'user'}, {'content': 'Answer: B \nExplanation: Question repeated', 'role': 'assistant'}]