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: Anatomy
False statement about type I respiratory failure is 
Select and explain. 
A. Decreased paO2, B. Decreased PaCO2, C. Normal PaCO2, D. Normal A-a gradient
D: Normal A-a gradient
Answer: D: Normal A-a gradient 
Explanation: Ref Harrison 19 th ed pg 1731 Type I respiratory failure is characterized by an increase in alveolar aerial O2 gradient,due to ventilation perfusion mismatch.