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: Medicine
[{'content': 'Which antibody is diagnostic of mixed connective tissue disease \nSelect and explain. \nA. Anti-histidyl t-RNA synthetase, B. Anti-U1-ribonucleoprotein, C. Anti-Myeloperoxidase, D. Anti-Proteinase-3', 'role': 'user'}, {'content': 'Answer: B \nExplanation: Anti-U1-ribonucleoprotein - MCTD\nAnti-histidyl t-RNA synthetase - Inflammatory myopathies.', 'role': 'assistant'}]