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: Radiology
[{'content': 'In CT scan CT number ranges from: \nSelect and explain. \nA. 0 to 1000, B. -1000 to +1000, C. 0 to 100, D. -100 to +100', 'role': 'user'}, {'content': 'Answer: B \nExplanation: “CT Scan” –\xa0 CT number ranges from – 1000 to +1000:\n\n– 1000 = air\xa0\xa0\xa0\xa0\n0 = water\n+ 1000 = bone (Dense)\n\nCT number is\xa0 called “Housefield number”.', 'role': 'assistant'}]