Final answer:
The most abundant cation in the ICF is potassium (K+).
Step-by-step explanation:
The most abundant cation in the intracellular fluid (ICF) is potassium (K+).
Most body fluids are neutral in charge, so cations and anions are balanced. In the ICF, potassium ions are concentrated inside cells. They are maintained at high levels by sodium-potassium pumps in the cell membranes, which use ATP to pump sodium out of the cell and potassium into the cell.