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
Stagnant hypoxia is seen in 
Select and explain. 
A. COPD, B. Anaemia, C. CO poisoning, D. Shock
D: Shock
Answer: D: Shock 
Explanation: Stagnant hypoxia, as its name implies, refers to situations in which blood flow is abnormally low as occurs in shock, syncope or other "low-flow" states. In terms of oxygen transpo, decreased blood flow (hypoperfusion) is the primary limitation, and thus, the problem resides with the cardiovascular system Ref: guyton and hall textbook of medical physiology 12 edition page number: 353,354,355