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': 'Spinnaker Sail sign is seen in \nSelect and explain. \nA. Pneumo mediastinium, B. Pseudo pneumo mediastinium, C. Pleural effusion, D. Pulmonary infarct', 'role': 'user'}, {'content': 'Answer: A \nExplanation: Pneumo mediastinium\n\nRing around the artery sign\nSpinnaker sail sign\nContinuous diaphragm sign', 'role': 'assistant'}]