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': 'Which one of the following is not a characteristic feature of rheumatoid ahritis ? \nSelect and explain. \nA. Sacroiliitis, B. Metacarpophalangeal joint involvement, C. Symmetrical ahritis, D. Positive rheumatoid factor', 'role': 'user'}, {'content': "Answer: A \nExplanation: Ans. is 'a' i.e., Sacroiliitis", 'role': 'assistant'}]