This is a real-world medical entrance exam question, please give the true answer based on the question and selection. Topic name: None, Subject name: Physiology
Fick's law is associated with which of the following functions? 
Select and explain. 
A. Osmosis, B. Phagocytosis, C. Diffusion, D. None of the above
C: Diffusion
Answer: C: Diffusion 
Explanation: The magnitude of the diffusing tendency from one region to another is directly propoionate to the cross-sectional area across which diffusion is taking place and the concentration gradient, or chemical gradient, which is the difference in concentration of the diffusing substance divided by the thickness of the boundary (Fick's law of diffusion). Ref: Ganong's Review of Medical Physiology 23rd edition, Chapter 1.