Standard Science Primary 5 Systems

When we inhale, what happens to the air in our lungs?

A Oxygen passes into the blood and carbon dioxide passes out of the blood.
B Nitrogen is completely absorbed by the lungs.
C Carbon dioxide passes into the blood and oxygen passes out.
D The air becomes drier and cooler.
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Worked Solution

Step 1: Inhaled air is rich in oxygen. Step 2: Gaseous exchange occurs at the air sacs (alveoli). Step 3: Oxygen enters the bloodstream for the body to use.

Correct answer: Oxygen passes into the blood and carbon dioxide passes out of the blood.

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