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': 'Which of the following will cause posterior impression on barium swallow: \nSelect and explain. \nA. ASD, B. VSD, C. Aberrant right subclavian artery, D. Pulmonary vascular hypertension', 'role': 'user'}, {'content': 'Answer: C \nExplanation: Aberrant right subclavian artery produces the classical appearance of a posterior impression on the proximal esophagus and left sided aortic arch impression.', 'role': 'assistant'}]