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
Predominant extracellular ions area) Na+b) K+c) Cl-d) HCO3-e) PO4- 
Select and explain. 
A. abc, B. ad, C. bc, D. acd
D: acd
Answer: D: acd 
Explanation: Predominant Ions
ECF- Na+, Cl-, HCO3-, Ca+2
 
ICF- K+, Mg+2, protein,  PO4-