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
Mottled enamel occurs due to: 
Select and explain. 
A. Fluorosis, B. Trauma, C. Hypocalcemia, D. Congenital syphilis
A: Fluorosis
Answer: A: Fluorosis 
Explanation: None