This is a real-world medical entrance exam question, please give the true answer based on the question and selection. Topic name: Pneumonia, Subject name: Medicine
[{'content': 'What is the probable diagnosis in the patient with below flow volume loop (FVL)? \nSelect and explain. \nA. Restrictive airway disease, B. Tracheal stenosis, C. Obstructive airway disease, D. None of the above', 'role': 'user'}, {'content': 'Answer: B \nExplanation: The above FVL is a typical of fixed central airway obstruction (Either above or below the thoracic inlet) such as tracheal stenosis. In this, there is limitation to peak flow rate,Flattened inspiratory and expiratory curves are seen. Other FVL patterns: 1.Normal 2. Airflow obstruction:- COPD 3. Fixed Upper Airway obstruction 4.Variable upper airway obstruction 5.', 'role': 'assistant'}]