This is a real-world medical entrance exam question, please give the true answer based on the question and selection. Topic name: Breast, Subject name: Pathology
Most common malignant bone tumor 
Select and explain. 
A. Osteogenic sarcotoma, B. Secondaries, C. Osteoma, D. Enchondroma
B: Secondaries
Answer: B: Secondaries 
Explanation: Primary bone tumors are considerably less common than bone metastases from other primary sites; metastatic disease is discussed at the end of this section. Primary bone tumors exhibit great morphologic diversity and clinical behaviors--from benign to aggressively malignant. ref : Robbins Basic Pathology, 9E,page-774