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
[{'content': 'In an average adult the distance between opening of sphenoid sinus and nasal spine is: \nSelect and explain. \nA. 5 cm, B. 6 cm, C. 7 cm, D. 8 cm', 'role': 'user'}, {'content': 'Answer: C \nExplanation: Anterior wall of sphenoid lies approximately 7 cm from anterior nasal spine at an angle of 30deg.', 'role': 'assistant'}]