This is a real-world medical entrance exam question, please give the true answer based on the question and selection. Topic name: Nose and paranasal sinuses, Subject name: ENT
[{'content': 'Most definitive diagnosis of sinusitis is \nSelect and explain. \nA. X-ray PNS, B. Proof puncture, C. Sinuscopy, D. Transillumination test', 'role': 'user'}, {'content': 'Answer: C \nExplanation: Sinuscopy or Diagnostic nasal endoscopy is the most appropriate investigation.The classical feature is the presence of mucopus in the middle meatus or above the middle meatusA more appropriate investigation would be CT scan of the nose and PNS.Ref: Hazarika; 3rd ed; Pg 331', 'role': 'assistant'}]