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
Acute lung injury in caused by all of the following except . 
Select and explain. 
A. Aspiration, B. Toxic gas inhalation, C. Cardiopulmonary bypass with hea lung machine., D. Lung contusion.
C: Cardiopulmonary bypass with hea lung machine.
Answer: C: Cardiopulmonary bypass with hea lung machine. 
Explanation: Answer is C (Cardiopulmonary bypass with hea lung machine): Cardiopulmonary bypass is a cause for indirect lung injury while the rest three cause direct injury to lungs. Although all four options may cause acute lung injury, the single best answer of exclusion would be cardiopulmonary bypass.