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
First permanent molars begin to calcify at: 
Select and explain. 
A. 6 months of intra uterine life, B. At birth, C. Before deciduous incisors, D. About 1 year after birth
B: At birth
Answer: B: At birth 
Explanation: None