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: Surgery
Gold standard diagnostic test in varicose veins is 
Select and explain. 
A. Photoplethysmography, B. Duplex imaging, C. Ultrasonography, D. Radio - labeled fibrinogen study
B: Duplex imaging
Answer: B: Duplex imaging 
Explanation: None