This is a real-world medical entrance exam question, please give the true answer based on the question and selection. Topic name: General physiology, Subject name: Physiology
Most diffusible ion across the membrane is 
Select and explain. 
A. Cl-, B. K+, C. Na+, D. Urea
B: K+
Answer: B: K+ 
Explanation: The resting membrane potential is close to the Nernst potential for K+, the ion to which the membrane is most permeable. .