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': 'What should be the length of post for posterior teeth: \nSelect and explain. \nA. Maximum 7mm below the canal orifice., B. Maximum 5 mm below the canal orifice., C. 2/3 to the root length., D. All of the above.', 'role': 'user'}, {'content': 'Answer: A \nExplanation: For anterior teeth post length should be 2/3-3/4of root length.', 'role': 'assistant'}]