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: Pathology
Most serious complication of Paget's disease: 
Select and explain. 
A. Osteochondroma., B. Osteosarcoma., C. Osteopetrosis., D. Osteitis deformans.
B: Osteosarcoma.
Answer: B: Osteosarcoma. 
Explanation: Development of osteosarcoma is the most serious complication of paget’s disease or osteitis deformans.