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: Surgery
[{'content': 'Which of the following are theories of regional Analgesia: \nSelect and explain. \nA. Specificity theory and Gate control theory, B. Specific receptor theory and Gate control theory, C. Specific receptor theory and Membrane expansion theory, D. Specificity theory and Membrane expansion theory', 'role': 'user'}, {'content': 'Answer: C \nExplanation: None', 'role': 'assistant'}]