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': 'Instrumentation well short of the apical foramen can result in: \nSelect and explain. \nA. Forcing necrotic material into the periapical region, B. Shelling or ledging the canal, C. Traumatizing the periapical tissues, D. Grossly enlarging the apical foramen', 'role': 'user'}, {'content': 'Answer: B \nExplanation: None', 'role': 'assistant'}]