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
Oxygen content of the arterial blood is reduced in all except- a) Methemoglobinemia  b) Fallot's tetralogy  c) Carbon monoxide poisoning  d) Fibrosing alveolitis 
Select and explain. 
A. ac, B. ad, C. ab, D. bd
A: ac
Answer: A: ac 
Explanation: None