This is a real-world medical entrance exam question, please give the true answer based on the question and selection. Topic name: Respiratory system, Subject name: Medicine
[{'content': 'Kerley B lines are due to- \nSelect and explain. \nA. Carcinoma bronchus, B. Pulmonary edema, C. Lung abscess, D. Pulmonary embolism', 'role': 'user'}, {'content': "Answer: B \nExplanation: In pulmonary oedema,chest X ray shows increased vascularity of the lung fields,and the right and left pulmonary aeries dilate.Subsequently,interstitial oedema causes thickened interlobular septa and dilated lymphatics.These are evident as horizontal lines in the costophrenic angles(septal or Kerley B lines). Reference:Davidson's medicine-22nd edition,page no:550.", 'role': 'assistant'}]