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: Dental
[{'content': 'A random sample suggests that \nSelect and explain. \nA. A person in a control group will not be a member of the experimental group, B. Any member of a group to be studied has an equal opportunity to be included in the study, C. Every nth name on a list is selected, D. Subjects are volunteers', 'role': 'user'}, {'content': 'Answer: B \nExplanation: None', 'role': 'assistant'}]