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': 'The best time to treat a cross-bite is: \nSelect and explain. \nA. When the roots are fully developed, B. When the roots are 2/3rd developed, C. Permanent dentition has completely erupted, D. As and when detected', 'role': 'user'}, {'content': 'Answer: D \nExplanation: None', 'role': 'assistant'}]