This is a real-world medical entrance exam question, please give the true answer based on the question and selection. Topic name: Respiratory System, Subject name: Physiology
The curve in question mark is caused by? 
Select and explain. 
A. Bronchial asthma, B. Emphysema, C. Pulmonary fibrosis, D. Chronic bronchitis
C: Pulmonary fibrosis
Answer: C: Pulmonary fibrosis 
Explanation: Ans. (c) Pulmonary fibrosis(Ref: Ganong, 25th ed/p.631)This is the pulmonary compliance curveIt is decreased (lower curve) in pulmonary fibrosisNormal curve is the middle curveIt is increased in emphysema (upper curve)