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: ENT
[{'content': 'Which is the MOST COMMON site for CSF Rhinorhoea? \nSelect and explain. \nA. Ethmoid sinus, B. Frontal sinus, C. Sphenoid sinus, D. Tegmen Tympani', 'role': 'user'}, {'content': 'Answer: A \nExplanation: The most common site of CSF leak are the lamina cribrosa and fovea ethmoidalis. CSF rhinorrhea may result from trauma, congenital anomalies, septal surgery or sinus surgery. It is typically intermittent and tends to be position dependent. Diagnosis is made by estimating the level of glucose in the sample. Glucose level of more than 50mg per 100ml is typically diagnostic. Presence of beta or tau transferrin is most specific for CSF rhinorrhea.', 'role': 'assistant'}]