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
Examine the shape of the flow volume curve carefully. This flow volume loop indicates one of the following: 
Select and explain. 
A. Normal, B. Extrathoracic obstruction, C. Intrathoracic obstruction, D. Fixed large airway obstruction
B: Extrathoracic obstruction
Answer: B: Extrathoracic obstruction 
Explanation: B i.e. Extrathoracic obstruction