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
In CT scan CT number ranges from: 
Select and explain. 
A. 0 to 1000, B. -1000 to +1000, C. 0 to 100, D. -100 to +100
B: -1000 to +1000
Answer: B: -1000 to +1000 
Explanation: “CT Scan” –  CT number ranges from – 1000 to +1000:

– 1000 = air    
0 = water
+ 1000 = bone (Dense)

CT number is  called “Housefield number”.