Final answer:
True, facilitated diffusion cannot transport molecules against a concentration gradient, as it moves substances from higher to lower concentration without energy.
Step-by-step explanation:
The statement that facilitated diffusion is unable to transport molecules against a concentration gradient is true. Facilitated diffusion involves the movement of molecules across a cell membrane via specific transport proteins without the use of cellular energy. This process moves substances down their concentration gradient, from a region of higher concentration to a region of lower concentration. Unlike facilitated diffusion, active transport requires energy to move molecules against their concentration gradient. An example of facilitated diffusion is the transfer of glucose into cells using glucose transporters.