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: Skin
[{'content': 'Reccurent oral ulcers with pain and erythematous halo around them, diagnosis is: \nSelect and explain. \nA. Apthus ulcer, B. Herpes, C. Chicken pox, D. Measels', 'role': 'user'}, {'content': 'Answer: A \nExplanation: A i.e. Apthous ulcer Apthous Ulcers Vitamine deficiency & Stress are impoant etiological agents Charecterstically presents with reccurent painful oral ulcers with erythema & halo around itQ.', 'role': 'assistant'}]