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
A patient with breathlessness shows Kerley B-lines in chest X-ray. These lines represents: 
Select and explain. 
A. Linear fibrosis, B. Haemosiderin deposits, C. Small focal atelectasis, D. Thickened interlobular septa
D: Thickened interlobular septa
Answer: D: Thickened interlobular septa 
Explanation: In pulmonary edema, as the pulmonary venous pressure increases, fluid leaks from the pulmonary capillaries into the adjacent interstitium. This interstitial pulmonary edema may be identified by peribronchial cuffing, indistinctness of the perivascular margins, perihilar haziness, and thickening of the interlobular septa and interlobar fissures. Septal thickening results in Kerley A (arrow) and Kerley B (arrowhead) lines on chest radiograph. Ref: Chiles C., Gulla S.M. (2011). Chapter 4. Radiology of the Chest. In M.Y. Chen, T.L. Pope, D.J. Ott (Eds), Basic Radiology, 2e.