This is a real-world medical entrance exam question, please give the true answer based on the question and selection. Topic name: Ultrasonography, CT, and MRI, Subject name: Radiology
[{'content': 'HU units value of bone - \nSelect and explain. \nA. 0, B. 40, C. -100, D. 1000', 'role': 'user'}, {'content': "Answer: D \nExplanation: Ans. is 'd' i.e., +1000 SubstanceHU unitsWaterDense cortical boneSoft tissueFatLung tissueAir0+ 1000 (+400 to + 1000)+ 40 to + 80- 60 to -100- 400 to -600- 1000", 'role': 'assistant'}]