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: Medicine
Most common cause of hypercapnic respiratory failure: March 2011,'Parch 2013 (a, b, h) 
Select and explain. 
A. Acute asthma, B. Aspergillosis, C. COPD, D. Pneumothorax
C: COPD
Answer: C: COPD 
Explanation: Ans. C: COPD Causes of type II (hypercapnic) respiratory failure: Chronic causes: COPD, sleep apnea, kyphscoliosis, myopathies/ muscular dystrophies, ankylosing spondylitis; Acute causes: Acute severe asthma (NOT acute asthma), acute exacerbation of COPD, upper airway obstruction, narcotic drugs etc. Type II respiratory failure: Reduced PaO2 Increased PaCO2 Normal P(A-a)O2 Hypoxemia with increased PaCO2 Type I respiratory failure: Reduced PaO2 Normal/ decreased PaCO2 INcreased P(A-a)O2 Hypoxemia with decreased PaCO2