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': 'A patient report to the dentist with trauma to immature tooth with open apex now dentist plan to do R.C.T. Best way to measure working length in this patient is by ? \nSelect and explain. \nA. Electronic apex locator, B. Radiographic method, C. Tactile method, D. Paper point', 'role': 'user'}, {'content': 'Answer: D \nExplanation: None', 'role': 'assistant'}]