This is a real-world medical entrance exam question, please give the true answer based on the question and selection. Topic name: Nose and PNS, Subject name: ENT
In an average adult the distance between opening of sphenoid sinus and nasal spine is: 
Select and explain. 
A. 5 cm, B. 6 cm, C. 7 cm, D. 8 cm
C: 7 cm
Answer: C: 7 cm 
Explanation: Anterior wall of sphenoid lies approximately 7 cm from anterior nasal spine at an angle of 30deg.