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
Earliest feature of pulmonary venous hypeension is - 
Select and explain. 
A. Upper lobar vessel dilatation, B. Kerley B Lines, C. Left atrial enlargement, D. Pleural effusion
A: Upper lobar vessel dilatation
Answer: A: Upper lobar vessel dilatation 
Explanation: 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.