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': 'On chronic treatment with a drug, a patient presents with gingival hyperplasia and facial hirsutism. The drug most likely to cause these side effects is : \nSelect and explain. \nA. Phenytoin, B. Carbamazepine, C. Valproic acid, D. Phenobarbitone', 'role': 'user'}, {'content': 'Answer: A \nExplanation: None', 'role': 'assistant'}]