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: Physiology
Cyanosis is not seen in 
Select and explain. 
A. CHF, B. COPD, C. CO poisoning, D. High altitude
C: CO poisoning
Answer: C: CO poisoning 
Explanation: Cyanosis is a bluish discoloration of the skin and mucous membranes resulting from inadequate oxygenation of the blood and not seen in CO poisoningRef: Hutchison&;s Clinical Methods, 23ed edition, page no: 21