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: Physiology
[{'content': '"Blood brain barrier" is present at all of the following sites except : \nSelect and explain. \nA. Hebenular nucleus, B. Subfornical organ, C. Cerebellum, D. Pontine nucleus', 'role': 'user'}, {'content': 'Answer: B \nExplanation: B i.e. Subfornical organ', 'role': 'assistant'}]