This is a real-world medical entrance exam question, please give the true answer based on the question and selection. Topic name: Respiratory, Subject name: Medicine
Floating water lilly sign on chest x-ray is characteristic of- 
Select and explain. 
A. Hydatid cyst, B. Lung abscess., C. Empyema thoracis, D. Ruptured amebic liver abscess
A: Hydatid cyst
Answer: A: Hydatid cyst 
Explanation: Ans. is 'a' i.e., Hydatid cyst o Floatine Water Lily Sien on Chest X-ray is characteristic sien of pulmonary cvstic echinococcosis or pulmonary hvdatid cvst.o It is seen when there is detachment of the endocystmembrane which results in floating membranes within the pericyst that mimics the appearance of water lily.