The correct option is B Causes net transport of molecules from low to high concentration
In facilitated diffusion, a carrier protein molecule moves a specific substance through the membrane along its concentration gradient. Since the movement is from a higher to a lower concentration, ATP is not used. When all the carrier molecules are being used, it is said to be saturated. Facilitated diffusion cannot cause net transport of molecules from a low to a high concentration, this would require an input of energy which is a characteristic of active transport.