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: Physiology
Carbon monoxide poisoning causes 
Select and explain. 
A. Hypoxic hypoxia, B. Oxygen dissociation curve shifts to left, C. Cyanosis, D. Diffusion capacity of lungs decreases
B: Oxygen dissociation curve shifts to left
Answer: B: Oxygen dissociation curve shifts to left 
Explanation: None