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
Root crown ratio of permanent teeth is about 
Select and explain. 
A. 2:01, B. 1:02, C. 4:01, D. 1:04
A: 2:01
Answer: A: 2:01 
Explanation: None