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: Unknown
Endoscopic sinus surgery prerequisite- 
Select and explain. 
A. MRI of paraanasal sinus, B. CT of PNS, C. Mucocilliary clearing testing, D. Acoustic tests
B: CT of PNS
Answer: B: CT of PNS 
Explanation: (Refer: PL Dhingra, Diseases of Ear, Nose & Throat, 7th edition, pg no. 220 – 221)

Endoscopic surgery of inflammatory diseases of paransal sinuses (sinusitis or polyp) requires a very detailed preoperative knowledge of the individual anatomical conditions and pathological changes
CT scan are used best to visualize sinus areas
CT scan provides excellent definition of paranasal sinuses and is a prerequisite for endoscopic surgery

“CT scan limited study coronal cuts in bone window is prerequisite for endscopic sinus surgery”-----Mohan Bansal