Final answer:
The size of the respiratory passages does not affect tissue gas exchange; factors like surface area, membrane thickness, and partial pressure differences are the main influences on gas exchange efficiency.
Step-by-step explanation:
The factor that does not affect the efficiency of tissue gas exchange is D. Size of the respiratory passages. The efficiency of gas exchange, which occurs due to simple diffusion, is primarily affected by: surface area of the respiratory membrane, thickness of the respiratory membrane, and partial pressure differences of gases. A large surface area increases the rate of diffusion, whereas a thicker membrane reduces it. The partial pressure differences drive the movement of gases across the membrane. However, the size of the respiratory passages primarily affects airway resistance but not tissue gas exchange itself.