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: Forensic Medicine
Commonest cause of thunderclap headache: AIIMS 10; NIMHANS 14 
Select and explain. 
A. Extradural hemorrhage, B. Aneursymal SAH, C. Subdural hemorrhage, D. Basilar migraine
B: Aneursymal SAH
Answer: B: Aneursymal SAH 
Explanation: Ans. Aneursymal SAH