Standard Science Primary 5 Systems

Which of the following correctly compares the air we breathe in and the air we breathe out?

A Breathed-out air has no oxygen left.
B Breathed-out air has more carbon dioxide and water vapour.
C Breathed-in air has no nitrogen.
D Breathed-out air has more oxygen.
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Worked Solution

Step 1: The body takes in oxygen and releases carbon dioxide as a waste product of respiration. Step 2: Water vapour is also released during exhalation. Step 3: Comparison shows higher CO2 and water vapour in exhaled air.

Correct answer: Breathed-out air has more carbon dioxide and water vapour.

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