Answer:
The correct option is: c. potassium
Step-by-step explanation:
In multicellular organisms, the extracellular fluid refers to the fluid which is present outside the cells of the body. The extracellular fluid mainly contains the sodium ions, bicarbonate ions and the chloride ions.
In multicellular organisms, the intracellular fluid is the fluid present inside the cells of the body. This intracellular fluid has high concentration of magnesium, phosphate and potassium ions.