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
True about Arrangement of hydroxyapatite crystals in Enamel rods? 
Select and explain. 
A. In center orientation of hydroxyapatite crystal is 0 degree, B. Orientation of hydroxyapatite crystals at periphery is 45 degree, C. Both, D. None
C: Both
Answer: C: Both 
Explanation: None