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': 'Recurrent oral ulcers with pain and erythematous halo around them, diagnosis is – \nSelect and explain. \nA. Apthous ulcer, B. Herpes, C. Chicken pox, D. Measels', 'role': 'user'}, {'content': 'Answer: A \nExplanation: Recurrent oral ulcers with erythematous halos suggest the diagnosis of Aphthous ulcer.', 'role': 'assistant'}]