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: Anatomy
[{'content': 'Lower esophageal sphincter: \nSelect and explain. \nA. Has no tonic activity, B. Has a tone which is provided by the sympathetic system, C. Relaxes on increasing abdominal pressure, D. Relaxes ahead of the peristaltic wave', 'role': 'user'}, {'content': 'Answer: D \nExplanation: D i.e. Relaxes ahead of the peristaltic wave', 'role': 'assistant'}]