<prompt>  A 40 year old female presents with a history of sudden onset of headache and nausea which passed off with rest and analgesics.Later she developed blurring of vision for a few days. On the day of admission she had developed third nerve palsy with neck rigidity. The temperature was 100F.The most likely diagnosis is -Acute attack of migraineViral encephalitisSub-arachnoid haemorrhageSevere hypertension 