This is a real-world medical entrance exam question, please give the true answer based on the question and selection. Topic name: C.N.S, Subject name: Medicine
[{'content': 'A patient presented with thunder clap headache. Followed by unconsciousness with progressive 3rd cranial nerve palsy \nSelect and explain. \nA. Extradual hemorrhage, B. Aneurysmal subarachnoid hemorrhage, C. Basilar migraine, D. Cluster Headache', 'role': 'user'}, {'content': "Answer: B \nExplanation: Harrison's textbook of internal medicine 17th edition . *Sudden transient loss of consciousness may be preceded by brief moment of excruciating head ache ,but most patient first complain of head ache on regain the consciousness . *3rd cranial nerve palsy , associate with pupillary dilatation,loss of ipsilateral light reflex,focal pain above and behind the eye . Ref Harrison20th edition pg 2445", 'role': 'assistant'}]