Final answer:
The ICF is characterized by high concentrations of potassium and proteins, distinguishing it from the ECF which is rich in sodium and chloride.
Step-by-step explanation:
The Intracellular Fluid (ICF) is the fluid contained within cells. It is rich in potassium (K+), magnesium (Mg²+), and proteins.
In contrast, the Extracellular Fluid (ECF), which includes both blood plasma and interstitial fluid (IF), has high concentrations of sodium (Na+) and chloride (Cl). Therefore, among the options provided, the one that best describes ICF is d. rich in proteins and K.