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': 'Which of the following is not an advantage of supragingival margin? \nSelect and explain. \nA. They can be easily finished, B. They are more easily kept clean, C. Provides additional retention, D. Restorations can be easily evaluated at recall appointments', 'role': 'user'}, {'content': 'Answer: C \nExplanation: When additional retention is required, subgingival finish line is indicated.', 'role': 'assistant'}]