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 principles of the cavity preparation is not considered much in modern methods of restorative Dentistry? \nSelect and explain. \nA. Extension for prevention, B. Convenient form, C. removal of the undermined enamel, D. Removal of the carious dentine', 'role': 'user'}, {'content': 'Answer: A \nExplanation: None', 'role': 'assistant'}]