This is a real-world medical entrance exam question, please give the true answer based on the question and selection. Topic name: ULTRASOUND, Subject name: Radiology
[{'content': 'All are hyperechoic on USG except \nSelect and explain. \nA. Air, B. Bone, C. Calcification, D. Bile', 'role': 'user'}, {'content': 'Answer: D \nExplanation: Bile is hypoechoic on USG. Air, bone, calcification and fat are hyperechoic on USG. Bile duct shown in the figure.', 'role': 'assistant'}]