This is a real-world medical entrance exam question, please give the true answer based on the question and selection. Topic name: Head & Neck, Subject name: Anatomy
[{'content': 'Which of the following sinus is related with middle ear cavity \nSelect and explain. \nA. Ethmoid, B. Cavernous, C. Transverse, D. Sigmoid', 'role': 'user'}, {'content': 'Answer: D \nExplanation: i.e. (Sigmoid sinus): (714,686 - Snell 8th)Sigmoid sinus are a direct continuation of the transverse sinuses. Each sinus turns downward behind the mastoid antrum of the temporal bone and then leaves the skull through the jugular foramen to become the internal jugular vein.* The posterior wall of the mastoid antrum is related to the sigmoid venous sinus. If the infection spreads in this direction a thrombosis in the sigmoid sinus may take place (714 - Snell 8th)', 'role': 'assistant'}]