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
Crown completion of Maxillary 2nd premolar occur 
Select and explain. 
A. At birth, B. 1 ½ year, C. 2 ½ to 3 year, D. 6-7 years
D: 6-7 years
Answer: D: 6-7 years 
Explanation: None