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': 'Butt joint is seen in: \nSelect and explain. \nA. 80%, B. 50%, C. 20%, D. 30%', 'role': 'user'}, {'content': 'Answer: D \nExplanation: Similarly gap joint at CEJ is seen in 10% of cases.', 'role': 'assistant'}]