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
A 25-years-old male had severe headache followed by unconsciousness. CSF tap revealed red blood cells. Most likely diagnosis is - 
Select and explain. 
A. Subdural hematoma, B. Embolism, C. Tumour, D. Ruptured aneurysm
D: Ruptured aneurysm
Answer: D: Ruptured aneurysm 
Explanation: None