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': 'All opens into coronary sinus except - \nSelect and explain. \nA. Middle cardiac vein, B. Small cardiac vein, C. Anterior cardiac vein, D. Great cardiac vein', 'role': 'user'}, {'content': 'Answer: C \nExplanation: Tributaries of the coronary sinus\n-\xa0\xa0\xa0\xa0\xa0\xa0\xa0 Great cardiac vein\n-\xa0\xa0\xa0\xa0\xa0\xa0\xa0 Middle cardiac vein\n-\xa0\xa0\xa0\xa0\xa0\xa0\xa0 Small cardiac vein\n-\xa0\xa0\xa0\xa0\xa0\xa0\xa0 Posterior vein of the left ventricle\n-\xa0\xa0\xa0\xa0\xa0\xa0\xa0 Oblique vein of the left atrium\n-\xa0\xa0\xa0\xa0\xa0\xa0\xa0 Right marginal vein sometimes.', 'role': 'assistant'}]