This is a real-world medical entrance exam question, please give the true answer based on the question and selection. Topic name: Tumors, Subject name: Orthopaedics
Which of the following tumour is associated with raised serum alkaline phosphatase levels? 
Select and explain. 
A. Osteoclastoma, B. Osteosarcoma, C. Multiple myeloma, D. Chondrosarcoma
B: Osteosarcoma
Answer: B: Osteosarcoma 
Explanation: Serum alkaline phosphatase (SAP) It is generally elevated, but is of no diagnostic significance. It has been considered a useful parameter for follow up of a case of osteosarcoma. A rise of SAP after an initial fall after tumour removal is taken as an indicator of recurrence or metastasis. Reference: Maheshwari; Essential Ohopaedics; Page no: 240