Which of the following statements about diffusion is true?

• A. Diffusion causes molecules to move from regions of lower concentration to regions of higher concentration until a gradient is established.
• B. Diffusion moves molecules only through membrane transport proteins and cannot occur directly through the lipid bilayer.
• C. Net movement of molecules occurs from regions of higher concentration to regions of lower concentration due to random thermal motion.
• D. Diffusion requires ATP hydrolysis to move molecules down their concentration gradient.

Answer: (C)