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': 'Crown root ratio in primary dentition is: \nSelect and explain. \nA. 1:04, B. 1:02, C. 1:03, D. 1:01', 'role': 'user'}, {'content': 'Answer: A \nExplanation: None', 'role': 'assistant'}]