How does facilitated diffusion differ from simple diffusion?

• A. Facilitated diffusion occurs only in prokaryotic cells, while simple diffusion occurs in all cell types.
• B. Facilitated diffusion requires energy, while simple diffusion does not.
• C. Facilitated diffusion involves specific membrane proteins, while simple diffusion does not.
• D. Facilitated diffusion moves solutes against their concentration gradient, while simple diffusion moves them down the gradient.

Answer: (C)