Which statement is the most accurate definition of external respiration?
A) Bulk flow (convection) of air or water to and from the gas-exchange membrane. B) The process by which O2 is transported to the gas-exchange membrane from the environmental medium and by which CO2 is transported away from the membrane into the environmental medium. C) The process by which CO2 is transported to the gas-exchange membrane from the environmental medium and O2 is transported away from the membrane into the environmental medium. D) Diffusion of O2 and CO2 across the gas exchange membrane.