In passive transport, how does increasing temperature affect the rate of diffusion of small molecules across a solution or membrane (assuming no phase change and constant concentration gradient)?

• A. It increases the diffusion rate because higher temperature increases molecules' kinetic energy and random motion.
• B. It stops diffusion by eliminating the concentration gradient.
• C. It decreases the diffusion rate because higher temperature increases viscosity in most aqueous solutions.
• D. It has no effect on diffusion rate because diffusion depends only on the concentration gradient.

Answer: (A)