This is a real-world medical entrance exam question, please give the true answer based on the question and selection. Topic name: Musculoskeletal Radiology, Subject name: Radiology
Sacrotuberous ligament calcification is a characteristic feature of? 
Select and explain. 
A. Alkaptonuria, B. Osteopetrosis, C. Fluorosis, D. Pseudogout
C: Fluorosis
Answer: C: Fluorosis 
Explanation: - Calcification of sacrotuberous ligament,interosseous ligaments is characteristic of Fluorosis