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': 'Deep vein thrombosis post-operatively is best diagnosed by \nSelect and explain. \nA. USG, B. Ascending venography, C. X-ray, D. Clinically', 'role': 'user'}, {'content': 'Answer: B \nExplanation: Ascending venography', 'role': 'assistant'}]