The Partial Pressure of Oxygen in the

Multiple Choice

The partial pressure of oxygen in the

A) atmospheric air averages 79% of total atmospheric pressure.
B) blood is the most important factor that determines the extent to which O₂ will combine with hemoglobin.
C) arterial blood is decreased when hemoglobin preferentially combines with CO rather than O₂.
D) both (a) and (b) above.
E) all of these answers.