Perfusion refers to the flow of blood to deliver O2 and nutrients to tissues and organs.

• A. Oxygenation
• B. Ventilation
• C. Perfusion
• D. Immunity

Answer: (C)

Perfusion is the flow of blood through the tissues and organs, delivering oxygen and nutrients and removing wastes. This is the mechanism by which the body’s cells actually receive the components they need to function; blood carries oxygen from the lungs and nutrients from the gut to every tissue.

Oxygenation, on the other hand, refers to how much oxygen is carried in the blood—its oxygen content—independent of how much blood is actually reaching tissues. Ventilation is the movement of air into and out of the lungs, enabling gas exchange but not describing blood flow. Immunity is the body's defense against pathogens and is not about blood flow to tissues.

Thus, perfusion best fits the definition: the circulation of blood delivering oxygen and nutrients to tissues and organs.