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 of the following statements about facilitated diffusion is true 
Select and explain. 
A. It is a form of active transport, B. It requires a carrier protein, C. Rate of transport is proportionate to the concentration gradient, D. Requires creatine phosphate
B: It requires a carrier protein
Answer: B: It requires a carrier protein 
Explanation: Facilitated diffusion is a form of passive transport which occurs along the concentration gradient, but requires a carrier protein.