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
Which of the following are theories of regional Analgesia: 
Select and explain. 
A. 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
C: Specific receptor theory and Membrane expansion theory
Answer: C: Specific receptor theory and Membrane expansion theory 
Explanation: None