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': 'The process by which controls are selected in such a way that they are similar to cases with regard to certain clinical variables in a case control study is known as \nSelect and explain. \nA. Confounding, B. Matching, C. Bias, D. Sampling', 'role': 'user'}, {'content': 'Answer: B \nExplanation: None', 'role': 'assistant'}]