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': 'Maximum radiation risk is present with: \nSelect and explain. \nA. OPG., B. MRI., C. CT scan., D. Ultrasonography.', 'role': 'user'}, {'content': 'Answer: C \nExplanation: MRI Thermography and ultrasonography (USG) contains no radiation risk because they use non-ionizing radiation.\nCT scan is whit maximum radiation risk', 'role': 'assistant'}]