Final answer:
The extracellular fluid is composed of interstitial fluid and plasma, with the interstitial fluid being the main component of the ECF, and plasma being the fluid component of blood.
Step-by-step explanation:
The extracellular fluid (ECF) is composed of interstitial fluid (IF) and plasma. Interstitial fluid is a solution that bathes and surrounds the cells of multicellular animals. It is the main component of the ECF, which also includes plasma and transcellular fluid. Plasma is the fluid part of the blood that transports cells, proteins, electrolytes, nutrients, gases, and wastes. It communicates with interstitial fluid through the capillary endothelium. Together, these fluids create the environment in which cells reside and function.
The intracellular fluid (ICF), on the other hand, lies within cells as the principal component of the cytosol/cytoplasm. Unlike ECF, ICF is the fluid enclosed within cells by their plasma membranes and makes up about 60 percent of the body's water content. Consequently, the correct answer to the question is A. interstitial fluid and plasma.