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: Surgery
[{'content': 'Which of the following venous sinuses is more likely to be affected with thrombosis in chronic otitis media and  mastoiditis? \nSelect and explain. \nA. Cavernous, B. Inter-Cavernous, C. Sigmoid, D. Superior petrosal', 'role': 'user'}, {'content': 'Answer: C \nExplanation: None', 'role': 'assistant'}]