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: ENT
[{'content': 'Gold standard test for diagnosis of laryngopharyngeal reflux is - \nSelect and explain. \nA. 24 hr double probe pH monitoring, B. Flexible endoscope, C. Barium swallow, D. Laryngoscopy', 'role': 'user'}, {'content': 'Answer: A \nExplanation: None', 'role': 'assistant'}]