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': "40 year old male farmer who has livestock was admitted with paroxysms of cough and expectoration. Clinical examination was normal. Chest X-ray showed a large thin walled cavity containing membranes in the lower lobe of the left lung with left pleural effusion. CT scan of the chest revealed a 'water lily' sign. What is the most probable diagnosis? \nSelect and explain. \nA. Echinococcus infection, B. Aspergillosis, C. Interstitial lung disease with TB, D. Amebic lung abscess", 'role': 'user'}, {'content': 'Answer: A \nExplanation: Water lily sign although rarely seen is pathognomonic of echinococcosis. Cyst with a freely floating endocyst.', 'role': 'assistant'}]