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
According to a newer hypothesis Ewings, sarcoma arises from - 
Select and explain. 
A. Epiphysis, B. Diaphysis, C. Medullary cavity, D. Cortex
C: Medullary cavity
Answer: C: Medullary cavity 
Explanation: Marrow tumors (medullary cavity tumors) : - Ewings sarcoma, Plasma cell tumor, multiple myeloma, Lymphoma.