Standard Science Primary 5 Systems

What is the main function of the air sacs (alveoli) in the lungs?

A To protect the lungs from dust.
B To allow for the exchange of gases.
C To produce oxygen for the body.
D To pump blood to the heart.
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Worked Solution

Step 1: The air sacs have very thin walls and are surrounded by blood vessels. Step 2: Oxygen passes from the air sacs into the blood. Step 3: Carbon dioxide passes from the blood into the air sacs to be exhaled.

Correct answer: To allow for the exchange of gases.

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