Standard Science Primary 5 Systems

Which of the following correctly describes the air we breathe OUT compared to the air we breathe IN?

A It has more oxygen and less carbon dioxide.
B It has less oxygen and more carbon dioxide.
C It has the same amount of nitrogen and oxygen.
D It contains no oxygen at all.
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Worked Solution

Step 1: During gas exchange in the lungs, oxygen enters the blood. Step 2: Carbon dioxide is released from the blood into the lungs. Step 3: Exhaled air therefore has lower oxygen and higher carbon dioxide content.

Correct answer: It has less oxygen and more carbon dioxide.

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