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': 'Greater vein of galen is formed by - \nSelect and explain. \nA. Superior sagittal sinus with straight sinus, B. Inferior sagittal sinus with straight sinus, C. Internal cerebral veins, D. Basilar vein', 'role': 'user'}, {'content': 'Answer: C \nExplanation: Great cerebral vein of Galen is formed by the union of two internal cerebral veins.', 'role': 'assistant'}]