This is a real-world medical entrance exam question, please give the true answer based on the question and selection. Topic name: Cardiovascular system, Subject name: Radiology
[{'content': 'Earliest feature of pulmonary venous hypeension is - \nSelect and explain. \nA. Upper lobar vessel dilatation, B. Kerley B Lines, C. Left atrial enlargement, D. Pleural effusion', 'role': 'user'}, {'content': 'Answer: A \nExplanation: Upper lobe venous diversion is the 1st radiological sign of pulmonary venous hypeension.Kerley B Lines , perihilar haze ,peribronchial cuffing,pumonary ossicles ,fine punctuate calcification and perihilar batwing pattern are the other features seen in PVH.', 'role': 'assistant'}]