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
At what age does calcification of the primary dentition begin? 
Select and explain. 
A. 6-10 weeks in utero, B. 13-16 weeks in utero, C. 22-26 weeks in utero, D. 30-34 weeks in utero
B: 13-16 weeks in utero
Answer: B: 13-16 weeks in utero 
Explanation: None