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 most common organism involved in a periapical abscess is: \nSelect and explain. \nA. Strep. pyogens, B. Strep. viridans, C. β hemolytic streptococci, D. Non hemolytic streptococci', 'role': 'user'}, {'content': 'Answer: A \nExplanation: None', 'role': 'assistant'}]