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 anatomic crown is shorter than the clinical crown of a tooth in which of the following instances: \nSelect and explain. \nA. Impaction, B. Gingivitis, C. Occlusal wear, D. Gingival recession', 'role': 'user'}, {'content': 'Answer: D \nExplanation: None', 'role': 'assistant'}]