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
Chronologic hypoplasia occur due to: 
Select and explain. 
A. Exanthematous diseases., B. Rickets., C. Hypoparathyroidism., D. No specific causes.
D: No specific causes.
Answer: D: No specific causes. 
Explanation: None