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': 'Bone Density is best studied by – \nSelect and explain. \nA. CT scan, B. DEXA scan, C. MRI scan, D. Bone scan', 'role': 'user'}, {'content': 'Answer: B \nExplanation: DEXA scan is the gold standard test for screening of bone density (to rule out asteoporosis).', 'role': 'assistant'}]