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
[{'content': 'Angular vein infection commonly causes thrombosis of: \nSelect and explain. \nA. Cavernous sinus, B. Sphenoid sinus, C. Petrosal sinus, D. Sigmoid sinus', 'role': 'user'}, {'content': 'Answer: A \nExplanation: Ref : Dhingra 7e pg 226.', 'role': 'assistant'}]