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

Step 1: The body takes in oxygen for respiration. Step 2: It produces carbon dioxide as a waste product. Step 3: Therefore, exhaled air has less oxygen (used by body) and more carbon dioxide (waste).

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

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