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: Pharmacology
[{'content': 'Leflunomide is used in the treatment of : \nSelect and explain. \nA. Rheumatoid arthritis, B. Dermatomyositis, C. Bony metastasis, D. Postmenopausal osteoporosis', 'role': 'user'}, {'content': 'Answer: A \nExplanation: None', 'role': 'assistant'}]