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': 'Persistant the cultures in a root canal is mostly due to \nSelect and explain. \nA. Seepage of saliva, B. Excessive instrumentation, C. Less medicament, D. Via apical foramina', 'role': 'user'}, {'content': 'Answer: A \nExplanation: None', 'role': 'assistant'}]