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': 'The side effect of phenytoin when its plasma concentration is above therapeutic level is : \nSelect and explain. \nA. Ataxia, B. Gum hypertrophy, C. Osteomalacia, D. Hirsutism', 'role': 'user'}, {'content': 'Answer: A \nExplanation: None', 'role': 'assistant'}]