This is a real-world medical entrance exam question, please give the true answer based on the question and selection. Topic name: Skeletal system, Subject name: Radiology
The gold standard for the diagnosis of osteoporosis is - 
Select and explain. 
A. Dual energy X-ray absorptiometry, B. Single energy X-ray absorptiometry, C. Ultrasound, D. Quantitative computed tomography
A: Dual energy X-ray absorptiometry
Answer: A: Dual energy X-ray absorptiometry 
Explanation: According to the osteoporosis guidelines for diagnosis and treatment, dual X-ray absorptiometry (DXA) represents the "gold standard" for diagnosis of osteoporosis and fracture risk prediction.