This is a real-world medical entrance exam question, please give the true answer based on the question and selection. Topic name: Gastro Intestinal System, Subject name: Pediatrics
[{'content': 'The Gold standard investigation for Gastro-esophageal reflux disease is: \nSelect and explain. \nA. Endoscopy, B. 24 hour pH recording, C. Oesophageal manometry, D. Measurement of length of lower oesophageal sphincter', 'role': 'user'}, {'content': "Answer: B \nExplanation: b. 24 hour pH recording(Ref: Nelson's 20/e p1787-1788, Ghai 8/e p 280)Extended esophageal pH monitoring of distal esophagus, provides a quantitative sensitive documentation of acidic reflux episodes, the most important type of reflux episodes for pathologic reflux", 'role': 'assistant'}]