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': 'Apical constriction is otherwise known as \nSelect and explain. \nA. Minor diameter, B. Major diameter, C. Radiographic apex, D. Tooth apex', 'role': 'user'}, {'content': 'Answer: A \nExplanation: None', 'role': 'assistant'}]