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': 'If posterior epistaxis cannot be controlled, which aery is ligated: \nSelect and explain. \nA. Posterior ethmoidal aery, B. Maxillary aery, C. Sphenopalatine aery, D. External carotid aery', 'role': 'user'}, {'content': 'Answer: C \nExplanation: Ligation technique is reserved for intractable bleeding where the source cannot be located or controlled by other techniques. The hierarchy of aeries used for ligation is: Sphenopalatine aery Internal maxillary aery External carotid Aery Anterior/posterior ethmoidal aery Earlier the most common aery ligated was maxillary aery but now endonasal sphenopalatine aery ligation (ESPAL) is the ligation of choice', 'role': 'assistant'}]