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
Maximum radiation risk is present with: 
Select and explain. 
A. OPG., B. MRI., C. CT scan., D. Ultrasonography.
C: CT scan.
Answer: C: CT scan. 
Explanation: MRI Thermography and ultrasonography (USG) contains no radiation risk because they use non-ionizing radiation.
CT scan is whit maximum radiation risk