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: Radiology
IOC for determing the etiology of sub arachnoid hemorrhage 
Select and explain. 
A. Non - contrast CT, B. CECT, C. Four vessel DSA, D. MRI
C: Four vessel DSA
Answer: C: Four vessel DSA 
Explanation: Four vessels (Both carotid and both vertebral) digital subtraction angiography is the IOC for determing the etiology of SAH.