Mira analyzed oxygen and carbon dioxide in inhaled and exhaled air. She found that the percentages of both gases were different in each. What other gas would most likely also have different amounts in inhaled and exhaled air?

Air leaving the lungs contains more water vapor than air being inhaled because it becomes warm and moist in the respiratory tract. Therefore, water vapor (H₂O) would also have different amounts in inhaled and exhaled air. Hydrogen, sulfur dioxide, and ozone are not normally produced in significant amounts during breathing.

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