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': 'Structures preserved\tin functional radical dissection of the neck, except \nSelect and explain. \nA. Internal jugular vein, B. Sternomastoid, C. Lymph nodes, D. Accessory nerve', 'role': 'user'}, {'content': 'Answer: C \nExplanation: None', 'role': 'assistant'}]