The composition of alveolar air differs from atmospheric air. Indicate all of the factors that account for this difference. A) Nitrogen does not enter alveoli B) Difference in overall (total) pressure C) Presence of water vapor D) Gas exchange adds CO₂ E) Gas exchange removes O₂

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The composition of alveolar air differs from atmospheric air mainly due to the presence of water vapor in the alveoli (C), the addition of carbon dioxide (CO2) from the blood into the alveoli (D), and the removal of oxygen (O2) from the alveoli into the blood (E). Nitrogen does enter the alveoli and the difference in overall pressure is not a factor in the composition difference.

The Composition of Alveolar Air Differs from Atmospheric Air