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: Surgery
[{'content': 'Best method to diagnose GERD is \nSelect and explain. \nA. Oesophageal pH determination, B. Endoscopy, C. Barium swallow, D. Laparoscopy', 'role': 'user'}, {'content': "Answer: A \nExplanation: 24 hours oesophageal pH monitoring is the gold standard investigation. PPI should be stopped for 3 weeks prior to pH monitoring. Dual probe pH monitoring(one in distal oesophagus and one in proximal oesophagus) is used to confirm the respiratory complication of GERD. Reference: SRB's Manual of Surgery, 6th Edition, page no= 782.", 'role': 'assistant'}]