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': 'A businessman who presented with substernal heaburn is diagnosed having gastroesophageal reflux disease (GERD). BEST test to diagnose GERD and quantify acid output is: \nSelect and explain. \nA. Esophagogram, B. Endoscopy, C. Manometry, D. 24 hour pH monitoring', 'role': 'user'}, {'content': "Answer: D \nExplanation: The most sensitive test for diagnosis of GERD is 24-h ambulatory pH monitoring. Endoscopy is indicated in patients with reflux symptoms refractory to antisecretory therapy; in those with alarming symptoms such as dysphagia, weight loss, or gastrointestinal bleeding; and in those with recurrent dyspepsia after treatment that is not clearly due to reflux on clinical grounds alone. Ref: Wong-Kee-Song L.M., Topazian M. (2012). Chapter 291. Gastrointestinal Endoscopy. In D.L. Longo, A.S. Fauci, D.L. Kasper, S.L. Hauser, J.L. Jameson, J. Loscalzo (Eds), Harrison's Principles of Internal Medicine, 18e.", 'role': 'assistant'}]