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
[{'content': "Which of the following sites is responsible for the amnestic defect in Wernicke's Korsakoff -syndrome - \nSelect and explain. \nA. Mamillary body, B. Thalamus, C. Subthalmic nucleus, D. Medical forc brain bundle", 'role': 'user'}, {'content': 'Answer: B \nExplanation: None', 'role': 'assistant'}]