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
Which law states that the amount of a substance crossing a given area is directly proportional to the area available for diffusion, concentration gradient and diffusion coefficient? 
Select and explain. 
A. Universal gas law, B. Dalton's law, C. Fick's law, D. All of the above
C: Fick's law
Answer: C: Fick's law 
Explanation: Fick Law of Diffusion:
Diffusion is well described by Fick law of diffusion. According to this law, amount of a substance crossing a given area is directly proportional to the area available for diffusion, concentration gradient and a constant known as diffusion coefficient.
Thus, 
Amount diffused = Area x Concentration gradient x Diffusion coefficient
Formula of Fick law: