This is a real-world medical entrance exam question, please give the true answer based on the question and selection. Topic name: Skeletal System, Subject name: Radiology
Marble bone is characteristic of? 
Select and explain. 
A. Osteopetrosis, B. Marfan's syndrome, C. Osteogenesis imperfecta, D. Melorheostosis
A: Osteopetrosis
Answer: A: Osteopetrosis 
Explanation: Ans AOsteopetrosis, also known as Marble bone disease, or Albers- Schonberg disease is an extremely rare inherited disorder whereby the bones harden, becoming denser due to defect in osteoclastic bone resorption.