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
Most definitive diagnostic of sinusitis is: 
Select and explain. 
A. X-ray PNS, B. Proof puncture, C. Nasal endoscopy, D. Transillumination test
C: Nasal endoscopy
Answer: C: Nasal endoscopy 
Explanation: 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.