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
Which is least common site of berry aneurysm - 
Select and explain. 
A. Basilar artery, B. Vertebral artery, C. Anterior cerebral artery, D. Posterior cerebral artery
B: Vertebral artery
Answer: B: Vertebral artery 
Explanation: None