Oxygen plays a minor role in control of normal respiration because
A. oxygenated blood is > 95% saturated.
B. deoxygenated venous blood is < 5% saturated.
C. oxygenated blood is more sensitive to CO₂.
D. deoxygenated venous blood is 75% saturated.
E. deoxygenated venous blood is polyunsaturated.