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: Medicine
25 year old weight lifter experienced sever headache during training. CSF tap done on the medical ward showed blood stains. What is the likely diagnosis? 
Select and explain. 
A. Cluster headache, B. Rupture aneurysm, C. Embolism, D. Migraine
B: Rupture aneurysm
Answer: B: Rupture aneurysm 
Explanation: The diagnosis is subarachnoid hemorrhage due to ruptured aneurysm. The term subarachnoid hemorrhage (SAH) refers to extravasation of blood into the subarachnoid space between the pial and arachnoid membranes. Intracranial saccular aneurysms ("berry aneurysms") represent the most common etiology of nontraumatic SAH; about 80% of cases of SAH result from ruptured aneurysms.The diagnosis is confirmed radiologically urgent CT scan without contrast.