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: Anaesthesia
[{'content': 'Site of action of epidural analgesia – \nSelect and explain. \nA. Sensory nerve ending, B. Ventral horn, C. Substantia gelatinosa, D. Cortex', 'role': 'user'}, {'content': 'Answer: C \nExplanation: Epidural opioid analgesics → act on opioid receptors present in substantia gelatinosa of dorsal horn cells.\nEpidural local anesthetics → act on nerve roots.', 'role': 'assistant'}]