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: Unknown
[{'content': 'All the following veins drain into internal jugular vein except \nSelect and explain. \nA. Facial vein, B. Lingual vein, C. Retromandibular vein, D. Superior thyroid vein', 'role': 'user'}, {'content': 'Answer: C \nExplanation: Retromandibular vein\nInternal Jugular vein\n\nIt is the continuation of sigmoid sinus\nTributaries of IJV\n\n1. Inferior Petrosal sinus\n2. Ferial\n3. Lingual\n4. Pharyngeal\n5. Superior thyroid vein\n6. Middle thyroid vein', 'role': 'assistant'}]