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: Surgery
Commonest malignant tumor of skeletal system ? 
Select and explain. 
A. Multiple myeloma, B. Metastasis, C. Osteosarcoma, D. Chondrosarcoma
B: Metastasis
Answer: B: Metastasis 
Explanation: Ans. is `b' i.e., Metastasis Commonest bone malignancies -Secondaries Commonest primary malignant tumor - A- Multiple myeloma Commonest primary malignant tumor - Osteosarcoma of long bones Commonest benign tumor of bone - - Osteochondroma (Osteochondroma is not true neoplasm since its growth stops with cessation of growth at the epiphyseal plate) Commonest true benign tumor of bone - Osteoid osteoma Commonest benign tumor of hand - Enchondroma