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
100% Oxygen is not effective in: March 2005 
Select and explain. 
A. Pulmonary edema, B. MI, C. Tetralogy of fallot, D. COPD
C: Tetralogy of fallot
Answer: C: Tetralogy of fallot 
Explanation: Ans. C: Tetralogy of fallot