This is a real-world medical entrance exam question, please give the true answer based on the question and selection. Topic name: Cell Physiology and Intercellular Connections, Subject name: Physiology
Most abundant extracellular ion is? 
Select and explain. 
A. Calcium, B. Potassium, C. Sodium, D. Chloride
C: Sodium
Answer: C: Sodium 
Explanation: ANSWER: (C) SodiumREF: Guyton's physiology 11th edition page 46, 358Repeat from June 2008 and December 2008Potassium is the most abundant cation in intracellular fluid.Phosphate is the most abundant intracellular anion.Sodium is the most abundant extracellular cation.Chloride is the most abundant extracellular anion.