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: Dental
[{'content': 'Most common side effect of phenytoin is: \nSelect and explain. \nA. Gingival hyperplasia, B. Dental stains, C. Hypertension, D. Gingival necrosis', 'role': 'user'}, {'content': 'Answer: A \nExplanation: Side Eﬀect Of Phenytoin\xa0\n\nHeadache\nNausea\nVomiting\xa0\nConstipation\xa0\nDizziness\nFeeling of spinning\xa0\nDrowsiness\nSwelling and bleeding of the gums\nTrouble in sleeping or nervousness may occur', 'role': 'assistant'}]