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: Pathology
[{'content': 'Anti U1-RNP antibody is seen in? \nSelect and explain. \nA. SLE, B. Scleroderma, C. MCTD, D. Dermatomyositis', 'role': 'user'}, {'content': 'Answer: C \nExplanation: “Absence of U1 RNP antibodies essentially rules out mixed connective tissue disorder”\nANTINUCLEAR ANTIBODY (ANA) PATTERNS AND CLINICAL ASSOCIATIONS', 'role': 'assistant'}]