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 incisor over-jet is increased for a class II case that is undergoing treatment. The reason is \nSelect and explain. \nA. Loss of anchorage, B. Arch collapse, C. Crowding in the lower arch, D. None of the above', 'role': 'user'}, {'content': 'Answer: A \nExplanation: None', 'role': 'assistant'}]