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: Anatomy
[{'content': 'Structure not enclosed by carotid sheath - \nSelect and explain. \nA. Internal carotid artery, B. Vagus, C. Cervical sympathetic chain, D. Internal jugular vein', 'role': 'user'}, {'content': 'Answer: C \nExplanation: Carotid sheath contains ICA, IJV and vagus nerve. In upper part of sheath there are IX, XI, XII nerves also.', 'role': 'assistant'}]