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': 'About test of significance between two large population, one of the following statements is true - \nSelect and explain. \nA. Null hypothesis states that 2 means are equal, B. Standard error of difference is the sum of the standard error of 2 means, C. Standard error of means are equal, D. Standard error of difference between populations calculated', 'role': 'user'}, {'content': 'Answer: D \nExplanation: None', 'role': 'assistant'}]