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
Most diffusable ion in excitable tissue is : 
Select and explain. 
A. Na., B. K., C. PO4, D. Cl
B: K.
Answer: B: K. 
Explanation: B i.e. K+ potassium ion is most diffusible ion