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': "All are chest x-ray signs of pulmonary embolism except \nSelect and explain. \nA. Westermark's sign, B. Felson's sign, C. Palla's sign, D. Monod sign", 'role': 'user'}, {'content': 'Answer: D \nExplanation: Monod sign - Aspergilloma.', 'role': 'assistant'}]