This is a real-world medical entrance exam question, please give the true answer based on the question and selection. Topic name: Oesophagus, Subject name: Surgery
[{'content': 'Gold Standard investigation for GERD- \nSelect and explain. \nA. 24 hour pH recording, B. Endoscopy, C. Ultrasound, D. Magnetic resonance imaging', 'role': 'user'}, {'content': "Answer: A \nExplanation: Ans. is 'a' i.e., 24 hour pH recording Diagnostic measurement in GERD* 24- hour pH recording is the 'gold standard' for diagnosis of GERD* TILOSRs are the most important manometric findings in GERD* The length and pressure of the LOS are also important", 'role': 'assistant'}]