This is a real-world medical entrance exam question, please give the true answer based on the question and selection. Topic name: Brain Imaging: Anatomy, Trauma, and Tumors, Subject name: Radiology
IOC for sub-arachnoid hemorrhage 
Select and explain. 
A. CT scan, B. MRI, C. Lumbar puncture, D. MRA
A: CT scan
Answer: A: CT scan 
Explanation: Ans. (a) CT scanRef.: Harrison 19th ed. /1786* The diagnosis of subarachnoid hemorrhage (SAH) usually depends on a high index of clinical suspicion combined with radiologic confirmation via urgent computed tomography (CT) scan without contrast.* Traditionally, a negative CT scan is followed with lumbar puncture (LP). However, non-contrast CT followed by CT angiography (CTA) of the brain can rule out SAH with greater than 99% sensitivity.