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': 'Lichen planus: \nSelect and explain. \nA. Can undergo malignant change, B. Treated only by medication, C. Must be excised, D. Is an idiosyncrasy reaction', 'role': 'user'}, {'content': 'Answer: A \nExplanation: None', 'role': 'assistant'}]