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': 'LES sphineter is relaxed by - \nSelect and explain. \nA. Nitrates, B. HL blockers, C. Morphine, D. All', 'role': 'user'}, {'content': "Answer: A \nExplanation: Answer is 'a' i.e. Nitrates", 'role': 'assistant'}]