Final answer:
Approximately 20% of the extracellular fluid comes from blood plasma, serving as a vital medium for transporting materials throughout the body.
Step-by-step explanation:
The question asks about the percentage of extracellular fluid (ECF) that comes from blood plasma. The ECF accounts for one-third of the body's water content, and 20 percent of this ECF is found in plasma. With these figures in mind, one can calculate that approximately 20 percent of the extracellular fluid comes from blood plasma, hence the correct answer to this question is C. 20%. Plasma is important because it travels through the body in blood vessels and transports a range of materials such as blood cells, proteins, nutrients, and wastes, all crucial for maintaining homeostasis.