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': '[?](pq/n) is \nSelect and explain. \nA. Standard error of propoions, B. Standard error of means, C. Standard error of propoions difference, D. Standard error of means difference', 'role': 'user'}, {'content': "Answer: A \nExplanation: Ref:Park's Textbook of Preventive and Social Medicine 25th Ed", 'role': 'assistant'}]