Which Does Not Apply to the Diffusion of O₂,CO₂ and Small

Multiple Choice

Which does not apply to the diffusion of O₂,CO₂ and small hydrophobic molecules across a membrane?

A) Diffusion is driven by the concentration gradient across the membrane.
B) The diffusion is spontaneous and there is a decrease in free energy as diffusion occurs.
C) The transport is saturable.
D) Membrane proteins are not needed for the diffusion process.