Each of the following factors affects the rate of external respiration except the
A) PO2 of the alveoli.
B) PCO2 of the blood.
C) thickness of the respiratory membrane.
D) PN2 of the alveoli.
E) solubility of oxygen in plasma.
Question 2
The human lens focuses light on the photoreceptor cells by
A) moving up and down.
B) moving in and out.
C) changing shape.
D) opening and closing.
E) dilating and constricting.