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: Pathology
[{'content': 'The bacteria observed as a causative organism in case of Recurrent apthous ulcers isq \nSelect and explain. \nA. Streptococcus sangius, B. Streptococcus mutans, C. Borellia vincentii, D. Staphylococci atbus', 'role': 'user'}, {'content': 'Answer: A \nExplanation: None', 'role': 'assistant'}]