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
The commonest extradural spinal tumour is ? 
Select and explain. 
A. Neurofibroma, B. Glioma, C. Meningioma, D. Metastasis
D: Metastasis
Answer: D: Metastasis 
Explanation: Ans. is 'd' i.e., Metastasis