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
All of the following investigations are needed for the diagnosis of osteosarcoma, except - 
Select and explain. 
A. MRI of femur, B. Bone marrow biopsy, C. Bone scan, D. CT chest
B: Bone marrow biopsy
Answer: B: Bone marrow biopsy 
Explanation: A biopsy of the lesion (not bone marrow biopsy) should always be carried out before commencing treatment.
Bone scan, MRI and CT chest are used.