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': 'Carotid artery stenosis screening invivo choice is : \nSelect and explain. \nA. USG, B. CT, C. MRI, D. Doppler', 'role': 'user'}, {'content': 'Answer: D \nExplanation: Color doppler ultrasonography is the screening method of choice (not simple USG : option a is incorrect).\nCarotid angiography is the investigation of choice for diagnosis.', 'role': 'assistant'}]