This is a real-world medical entrance exam question, please give the true answer based on the question and selection. Topic name: CT SCAN, Subject name: Radiology
[{'content': 'Which of the following has Higher Hounsfield Unit? \nSelect and explain. \nA. CSF, B. Fat, C. Air, D. Grey matter', 'role': 'user'}, {'content': 'Answer: D \nExplanation: None', 'role': 'assistant'}]