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
The bacteria observed as a causative organism in case of Recurrent apthous ulcers isq 
Select and explain. 
A. Streptococcus sangius, B. Streptococcus mutans, C. Borellia vincentii, D. Staphylococci atbus
A: Streptococcus sangius
Answer: A: Streptococcus sangius 
Explanation: None