In CT scan CT number ranges from:: (A) 0 to 1000, (B) -1000 to +1000, (C) 0 to 100, (D) -100 to +100
Answer is B. “CT Scan” –  CT number ranges from – 1000 to +1000:

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

CT number is  called “Housefield number”.