This is a real-world medical entrance exam question, please give the true answer based on the question and selection. Topic name: Head and neck, Subject name: Surgery
[{'content': 'Structures not removed in radical neck dissection \nSelect and explain. \nA. X nerve, B. XI nerve, C. Tail of parotid, D. Parotid and post-auricular nerve', 'role': 'user'}, {'content': 'Answer: A \nExplanation: The classic operation involves resection of the cervical lymphatics and lymph nodes and those structures closely associated: the internal jugular vein, the accessory nerve, the submandibular gland and the sternocleidomastoid muscle. These structures are all removed en blocand in continuity with the primary disease if possible. The main disability that follows the operation is weakness and drooping of the shoulder due to paralysis of the trapezius muscle as a consequence of excision of the accessory nerve Bailey & Love ,25th,733.', 'role': 'assistant'}]