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': 'Earliest sign of pulmonary venus hypeension on chest radiograph is: \nSelect and explain. \nA. Pleural effusion, B. Kerley B lines, C. Cephalization of veins, D. Kerley a lines', 'role': 'user'}, {'content': 'Answer: C \nExplanation: Ans. Cephalization of veins', 'role': 'assistant'}]