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
[{'content': 'What diagnosis is suggested by these spirography findings? \nSelect and explain. \nA. Intrathoracic localized obstruction, B. Fixed inspiratory obstruction, C. Pneumothorax, D. Restrictive lung disease', 'role': 'user'}, {'content': 'Answer: A \nExplanation: Answer A. Intrathoracic localized obstructionAn intrathoracic localized obstruction is demonstrated on spirography. The patient underwent flexible fiberoptic bronchoscopy, which revealed nearly complete (greater than 90%) occlusion of the distal trachea by a vascular mass. The patient recovered after endoscopic laser ablation of the mass.', 'role': 'assistant'}]