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
All of the following transport processes follow 'saturation kinetics' except 
Select and explain. 
A. Facilitated diffusion, B. Na+  - Ca2+ exchanger, C. Simple diffusion, D. Na+ coupled active transport
C: Simple diffusion
Answer: C: Simple diffusion 
Explanation: Saturation kinetics is seen in transport mechanisms that utilize carrier proteins. In passive transport mechanisms, there is no carrier protein.