This is a real-world medical entrance exam question, please give the true answer based on the question and selection. Topic name: Regional Anesthesia, Subject name: Anaesthesia
[{'content': 'Which of the following is most sensitive to the inhibition by local anesthetics - \nSelect and explain. \nA. B fibre, B. Dorsal root, C. As, D. Aa', 'role': 'user'}, {'content': 'Answer: A \nExplanation: Sensitivity of nerve fibres to inhibition by local anesthetics is determined by axonal diameter, myelination and other anatomical & physiological features. In comparing nerve fibers of the serve type smaller diameter increases sensitivity to local anesthetics. Thus larger Aa fibres less sensitive to local anesthetics then smaller, slower conducting As fibres. For sensitivity B>C=Adelta>Agama>Ab>Aa Most sensitive - Least sensitive for L.A. B>C>A Autonomic > Sensory > Motor Temperature (Cold) >Pain> Touch> proprioception Recovery from block is in opposite direction', 'role': 'assistant'}]