This is a real-world medical entrance exam question, please give the true answer based on the question and selection. Topic name: G.I.T., Subject name: Physiology
[{'content': 'Length of lower esophageal sphincter- \nSelect and explain. \nA. 1-2 cm, B. 3-4 cm, C. 1-2 mm, D. 3-4 mm', 'role': 'user'}, {'content': 'Answer: B \nExplanation: Ans. is \'b\' i.e., 3-4 cm "The cricopharyngeal sphincter is 2-3 cm, and the lower esophageal sphincter (LES) is 3-4 cm long" -- Textbook of GI Surgery* Approximately 2 cm of the esophagus lie below the diaphragm in the abdomen (abdominal part of esophagus).* Within this portion of esophagus the abdominal part of LES is located.* Another 1-2 cm of LES lie above the diaphragm in mediastinum, i.e. thoracic part of LES.* Thus total length of LES is 3-4 cm.', 'role': 'assistant'}]