This is a real-world medical entrance exam question, please give the true answer based on the question and selection. Topic name: Paranasal Sinuses, Subject name: ENT
[{'content': 'Most definitive diagnostic of sinusitis is: \nSelect and explain. \nA. X-ray PNS, B. Proof puncture, C. Nasal endoscopy, D. Transillumination test', 'role': 'user'}, {'content': 'Answer: C \nExplanation: Nasal endoscopy is the most definitive diagnostic of sinusitis. It is done to see the various sinus meatuses, mucopus or any other pathology. If mucopus is seen in the meatus, it is confirmatory of sinusitis.', 'role': 'assistant'}]