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
A 2 year old child with purulent nasal discharge,fever and pain since 2 months. His fever is 102-103 F, and leucocyte count is 12000 cu/mm.X ray PNS showed opacification of left ethmoidal air cells.The culture of the eye discharge was negative. which of the following would be most useful fuher step in evaluation of this patient? 
Select and explain. 
A. CT Scan, B. Urine culture, C. Blood culture, D. Repeat culture of the eye discharge
A: CT Scan
Answer: A: CT Scan 
Explanation: The best method to assess the state of ethmoidal air cells and it's complications is CT Scan. "CT is paicularly useful in ethmoid and sphenoid sinus infections and has replaced studies with contrast material". Ref Dhingra 5/e,p 209.