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: Orthopaedics
Bone forming tumors are -a) Osteosarcomab) Osteoid osteomac) Giant cell tumourd) Osteoblastomae) Chondrosarcoma 
Select and explain. 
A. abd, B. bcd, C. abc, D. ab
A: abd
Answer: A: abd 
Explanation: Bone forming tumors 

Benign : - Osteoma, Osteoid osteoma, Osteoblastoma.
Malignant : - Osteosarcoma