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: Physiology
[{'content': 'Examine the shape of the flow volume curve carefully. This flow volume loop indicates one of the following: \nSelect and explain. \nA. Normal, B. Extrathoracic obstruction, C. Intrathoracic obstruction, D. Fixed large airway obstruction', 'role': 'user'}, {'content': 'Answer: B \nExplanation: B i.e. Extrathoracic obstruction', 'role': 'assistant'}]