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': 'Contents of posterior triangle of neck \nSelect and explain. \nA. Occipital artery, spinal accessory nerve, hypoglossal, ascending pharyngeal artery, B. Occipital artery, lesser occipital nerve, subclavian artery, spinal accessory nerve, C. Occipital artery, spinal accessory nerve, subclavian artery, hypoglossal nerve, D. Occipital artery, Lesser occipital nerve, ascending pharyngeal artery, vagus nerve', 'role': 'user'}, {'content': 'Answer: B \nExplanation: Contents of posterior triangle of neck :\n\nOccipital artery.\nSpinal accessory nerve.\nSubclavian vessels.\nTrunks of brachial plexus.\nGreat auricular nerve, lesser occipital nerve, supraclavicular nerve, transverse cutaneous nerve.\nExternal jugular vein.', 'role': 'assistant'}]