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: Radiology
"Marble bone" appearance is characteristic of: 
Select and explain. 
A. Osteopetrosis, B. Osteogenesis imperfecta, C. Fluorosis, D. Achondroplasia
A: Osteopetrosis
Answer: A: Osteopetrosis 
Explanation: Ans. Osteopetrosis