Final answer:
The electrolytes with the highest concentration in the ICF are potassium (K+) and phosphate (HPO₄⁻²), maintained by active transport mechanisms like the sodium-potassium pump.
Step-by-step explanation:
The two electrolytes in greatest concentration in the Intracellular Fluid (ICF) are potassium (K+) and phosphate (HPO₄⁻²). While sodium (Na+) and chloride (Cl⁻) ions are concentrated in the Extracellular Fluid (ECF), the ICF is characterized by high levels of potassium and phosphate.
These concentrations are maintained by mechanisms such as the sodium-potassium pump, which actively transports sodium out of the cell and potassium into the cell.