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
Early change of pulmonary edema in CXR: 
Select and explain. 
A. Batswing appearance, B. Pleural effusion, C. Kerley B lines, D. Ground gram lung field
C: Kerley B lines
Answer: C: Kerley B lines 
Explanation: Ans. Kerley B lines